diff --git a/.github/workflows/ci_gcc.yml b/.github/workflows/ci_gcc.yml
index 054270ab..2927759b 100644
--- a/.github/workflows/ci_gcc.yml
+++ b/.github/workflows/ci_gcc.yml
@@ -13,7 +13,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        version: [L] # [H, I, I_patch, J, K, L]
+        version: [K, L] # [H, I, I_patch, J, K, L]
         suffix: [~, _d, _rom]
 
     steps:
@@ -32,7 +32,7 @@ jobs:
         token: ${{ secrets.SECRETTOKEN }}
         path: deps_repo
     - name: Get the dependency
-      run: cp deps_repo/libultra/${{ matrix.version }}/* .
+      run: cp deps_repo/libultra/${{ matrix.version }}/* base/${{ matrix.version }}
 
     - name: Setup
       run: make setup -j $(nproc) TARGET=libgultra${{ matrix.suffix }} VERSION=${{ matrix.version }}
diff --git a/.github/workflows/ci_ido.yml b/.github/workflows/ci_ido.yml
index 4d7f8dca..dd12a67a 100644
--- a/.github/workflows/ci_ido.yml
+++ b/.github/workflows/ci_ido.yml
@@ -13,7 +13,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        version: [L] # [E, F, G, H, I, I_patch, J, K, L]
+        version: [K, L] # [E, F, G, H, I, I_patch, J, K, L]
         suffix: [~, _rom] # [~, _d, _rom]
 
     steps:
@@ -32,7 +32,7 @@ jobs:
         token: ${{ secrets.SECRETTOKEN }}
         path: deps_repo
     - name: Get the dependency
-      run: cp deps_repo/libultra/${{ matrix.version }}/* .
+      run: cp deps_repo/libultra/${{ matrix.version }}/* base/${{ matrix.version }}
 
     - name: Setup
       run: make setup -j $(nproc) TARGET=libultra${{ matrix.suffix }} VERSION=${{ matrix.version }}
diff --git a/Makefile b/Makefile
index cf87da47..6ef95ed8 100644
--- a/Makefile
+++ b/Makefile
@@ -4,12 +4,13 @@ NON_MATCHING ?= 0
 # libgultra_rom, libgultra_d, libgultra
 # libultra_rom, libultra_d, libultra
 TARGET ?= libgultra_rom
+VERSION ?= L
 CROSS ?= mips-linux-gnu-
 
-BASE_DIR := base_$(TARGET)
-BASE_AR := $(TARGET).a
+BASE_DIR := extracted/$(VERSION)/$(TARGET)
+BASE_AR := base/$(VERSION)/$(TARGET).a
 BUILD_ROOT := build
-BUILD_DIR := $(BUILD_ROOT)/$(TARGET)
+BUILD_DIR := $(BUILD_ROOT)/$(VERSION)/$(TARGET)
 BUILD_AR := $(BUILD_DIR)/$(TARGET).a
 
 WORKING_DIR := $(shell pwd)
@@ -17,6 +18,18 @@ WORKING_DIR := $(shell pwd)
 CPP := cpp -P
 AR := ar
 
+VERSION_D := 1
+VERSION_E := 2
+VERSION_F := 3
+VERSION_G := 4
+VERSION_H := 5
+VERSION_I := 6
+VERSION_J := 7
+VERSION_K := 8
+VERSION_L := 9
+
+VERSION_DEFINE := -DBUILD_VERSION=$(VERSION_$(VERSION)) -DBUILD_VERSION_STRING=\"2.0$(VERSION)\"
+
 ifeq ($(findstring libgultra,$(TARGET)),libgultra)
 -include Makefile.gcc
 else ifeq ($(findstring libultra,$(TARGET)),libultra)
@@ -40,8 +53,7 @@ ASM_DIRS := $(shell find asm -type d -not -path "asm/non_matchings*")
 C_FILES  := $(foreach dir,$(SRC_DIRS),$(wildcard $(dir)/*.c))
 S_FILES  := $(foreach dir,$(SRC_DIRS) $(ASM_DIRS),$(wildcard $(dir)/*.s))
 O_FILES  := $(foreach f,$(S_FILES:.s=.o),$(BUILD_DIR)/$f) \
-            $(foreach f,$(C_FILES:.c=.o),$(BUILD_DIR)/$f) \
-            $(foreach f,$(wildcard $(BASE_DIR)/*),$(BUILD_DIR)/$f)
+            $(foreach f,$(C_FILES:.c=.o),$(BUILD_DIR)/$f)
 # Because we patch the object file timestamps, we can't use them as the targets since they'll always be older than the C file
 # Therefore instead we use marker files that have actual timestamps as the dependencies for the archive
 MARKER_FILES := $(O_FILES:.o=.marker)
@@ -61,6 +73,17 @@ AR_OLD := $(AR)
 endif
 
 BASE_OBJS := $(wildcard $(BASE_DIR)/*.o)
+
+# Check to make sure the current version has been set up
+ifneq ($(NON_MATCHING),1)
+ifeq ($(BASE_OBJS),)
+# Ignore this check if the user is currently running setup, clean or distclean
+ifeq ($(filter $(MAKECMDGOALS),setup clean distclean),)
+$(error Current version ($(TARGET) 2.0$(VERSION)) has not been setup!)
+endif
+endif
+endif
+
 # Try to find a file corresponding to an archive file in any of src/ asm/ or the base directory, prioritizing src then asm then the original file
 AR_ORDER = $(foreach f,$(shell $(AR) t $(BASE_AR)),$(shell find $(BUILD_DIR)/src $(BUILD_DIR)/asm $(BUILD_DIR)/$(BASE_DIR) -iname $f -type f -print -quit))
 MATCHED_OBJS = $(filter-out $(BUILD_DIR)/$(BASE_DIR)/%,$(AR_ORDER))
@@ -69,7 +92,7 @@ NUM_OBJS = $(words $(AR_ORDER))
 NUM_OBJS_MATCHED = $(words $(MATCHED_OBJS))
 NUM_OBJS_UNMATCHED = $(words $(UNMATCHED_OBJS))
 
-$(shell mkdir -p asm $(BASE_DIR) src $(BUILD_DIR)/$(BASE_DIR) $(foreach dir,$(ASM_DIRS) $(SRC_DIRS),$(BUILD_DIR)/$(dir)))
+$(shell mkdir -p asm $(BASE_DIR) src $(foreach dir,$(ASM_DIRS) $(SRC_DIRS),$(BUILD_DIR)/$(dir)))
 
 .PHONY: all clean distclean setup
 all: $(BUILD_AR)
@@ -85,15 +108,15 @@ ifneq ($(NON_MATCHING),1)
 endif
 
 clean:
-	$(RM) -rf $(BUILD_ROOT)
+	$(RM) -rf $(BUILD_DIR)
 
-distclean: clean
+distclean:
 	$(MAKE) -C tools distclean
-	$(RM) -rf $(BASE_DIR)
+	$(RM) -rf extracted/ $(BUILD_ROOT)
 
 setup:
 	$(MAKE) -C tools
-	cd $(BASE_DIR) && $(AR) xo ../$(BASE_AR)
+	cd $(BASE_DIR) && $(AR) xo $(WORKING_DIR)/$(BASE_AR)
 	chmod -R +rw $(BASE_DIR)
 ifeq ($(COMPILER),ido)
 	export CROSS=$(CROSS) && ./tools/strip_debug.sh $(BASE_DIR)
diff --git a/Makefile.gcc b/Makefile.gcc
index dce908b0..0cb3f6ee 100644
--- a/Makefile.gcc
+++ b/Makefile.gcc
@@ -9,7 +9,7 @@ export COMPILER_PATH := $(WORKING_DIR)/tools/gcc
 
 CFLAGS := -w -nostdinc -c -G 0 -mgp32 -mfp32 -D_LANGUAGE_C
 ASFLAGS := -w -nostdinc -c -G 0 -mgp32 -mfp32 -DMIPSEB -D_LANGUAGE_ASSEMBLY -D_MIPS_SIM=1 -D_ULTRA64 -x assembler-with-cpp
-CPPFLAGS = -D_MIPS_SZLONG=32 -D__USE_ISOC99 $(GBIDEFINE)
+CPPFLAGS = -D_MIPS_SZLONG=32 -D__USE_ISOC99 $(GBIDEFINE) $(VERSION_DEFINE)
 IINC = -I . -I $(WORKING_DIR)/include -I $(WORKING_DIR)/include/gcc -I $(WORKING_DIR)/include/PR
 MIPS_VERSION := -mips3
 ASOPTFLAGS :=
diff --git a/Makefile.ido b/Makefile.ido
index 54c8ff78..8cfb28fe 100644
--- a/Makefile.ido
+++ b/Makefile.ido
@@ -9,7 +9,7 @@ export COMPILER_PATH := $(WORKING_DIR)/tools/ido
 
 CFLAGS := -c -Wab,-r4300_mul -G 0 -nostdinc -Xcpluscomm -fullwarn -woff 516,649,838,712
 ASFLAGS := -c -Wab,-r4300_mul -G 0 -nostdinc -woff 516,649,838,712
-CPPFLAGS = -D_MIPS_SZLONG=32 $(GBIDEFINE) $(PICFLAGS)
+CPPFLAGS = -D_MIPS_SZLONG=32 $(GBIDEFINE) $(VERSION_DEFINE) $(PICFLAGS)
 IINC = -I $(WORKING_DIR)/include -I $(WORKING_DIR)/include/ido -I $(WORKING_DIR)/include/PR
 MIPS_VERSION := -mips2 -o32
 PICFLAGS := -non_shared
diff --git a/README.md b/README.md
index ce88d5cb..0f7eaddb 100644
--- a/README.md
+++ b/README.md
@@ -15,13 +15,15 @@ Currently this repo supports building the following versions:
 | 2.0I       | :x: / :x: | :x: / :x: | :x: / :x: |
 | 2.0I_patch | :x: / :x: | :x: / :x: | :x: / :x: |
 | 2.0J       | :x: / :x: | :x: / :x: | :x: / :x: |
-| 2.0K       | :x: / :x: | :x: / :x: | :x: / :x: |
+| 2.0K       | :heavy_check_mark: / :heavy_check_mark: | :x: / :heavy_check_mark: | :heavy_check_mark: / :heavy_check_mark: |
 | 2.0L       | :heavy_check_mark: / :heavy_check_mark: | :x: / :heavy_check_mark: | :heavy_check_mark: / :heavy_check_mark: |
 | ique_v1.5  | :x: | :x: | :x: |
 
 ## Preparation
 
-After cloning the repo, put a copy of the target archive on the root of this directory.
+After cloning the repo, put a copy of the target archive(s) in their correct version folder in `base/`.
+For example, if your target archive is libgultra_rom.a 2.0L then you'd place it in `base/L/`.
+If you will be building without a target archive by setting `NON_MATCHING` then you can skip this step.
 
 ## Build dependencies
 
@@ -46,5 +48,12 @@ sudo apt install binutils-mips-linux-gnu
 
 ## Building
 
-- `make setup`
-- `make`
+Run make setup with the proper flags set followed by make with optional jobs.
+For example, if building the 2.0L PC archive you'd do the following: 
+
+- `make VERSION=L TARGET=libgultra_rom setup`
+- `make VERSION=L TARGET=libgultra_rom`
+
+Every target flag combination requires separate a setup command.
+
+If building without a target archive using `NON_MATCHING` then you can skip the setup command.
diff --git a/base/J/.gitkeep b/base/J/.gitkeep
new file mode 100644
index 00000000..e69de29b
diff --git a/base/K/.gitkeep b/base/K/.gitkeep
new file mode 100644
index 00000000..e69de29b
diff --git a/base/L/.gitkeep b/base/L/.gitkeep
new file mode 100644
index 00000000..e69de29b
diff --git a/include/PR/os_version.h b/include/PR/os_version.h
index c485a438..aa10d20e 100644
--- a/include/PR/os_version.h
+++ b/include/PR/os_version.h
@@ -10,7 +10,17 @@
 #ifndef _OS_VERSION_H_
 #define	_OS_VERSION_H_
 
-#define OS_MAJOR_VERSION	"2.0K"	/* major version */
-#define OS_MINOR_VERSION	0	/* patch level */
+#define VERSION_D 1
+#define VERSION_E 2
+#define VERSION_F 3
+#define VERSION_G 4
+#define VERSION_H 5
+#define VERSION_I 6
+#define VERSION_J 7
+#define VERSION_K 8
+#define VERSION_L 9
+
+#define OS_MAJOR_VERSION	BUILD_VERSION_STRING /* major version */
+#define OS_MINOR_VERSION	0 /* patch level */
 
 #endif /* !_OS_VERSION_H_ */
diff --git a/src/debug/threadprofilestop.c b/src/debug/threadprofilestop.c
index 7cc20e7a..4803620b 100644
--- a/src/debug/threadprofilestop.c
+++ b/src/debug/threadprofilestop.c
@@ -10,8 +10,13 @@ void osThreadProfileStop(void) {
 
 #ifndef NDEBUG
     if (__osThprofFlag == 0) {
+#if BUILD_VERSION >= VERSION_L
         __osRestoreInt(saveMask);
         __osError(138, 0);
+#else
+        __osError(138, 0);
+        __osRestoreInt(saveMask);
+#endif
         return;
     }
 #endif
@@ -23,9 +28,13 @@ void osThreadProfileStop(void) {
             thprof[id].time += now_time - __osThprofLastTimer;
         } else {
 #ifndef NDEBUG
+#if BUILD_VERSION >= VERSION_L
             __osRestoreInt(saveMask);
+#endif
             __osError(147, 1, id);
+#if BUILD_VERSION >= VERSION_L
             saveMask = __osDisableInt();
+#endif
 #endif
         }
     }
diff --git a/src/io/conteepprobe.c b/src/io/conteepprobe.c
index 5bee6a4b..b19dc495 100644
--- a/src/io/conteepprobe.c
+++ b/src/io/conteepprobe.c
@@ -26,7 +26,9 @@ s32 osEepromProbe(OSMesgQueue* mq) {
         }
     }
 
+#if BUILD_VERSION >= VERSION_L
     __osEepromRead16K = 0;
+#endif
     __osSiRelAccess();
     return ret;
 }
diff --git a/src/io/conteepread.c b/src/io/conteepread.c
index 708a9768..8334382a 100644
--- a/src/io/conteepread.c
+++ b/src/io/conteepread.c
@@ -4,7 +4,9 @@
 #include "siint.h"
 
 OSPifRam __osEepPifRam ALIGNED(16);
+#if BUILD_VERSION >= VERSION_L
 s32 __osEepromRead16K;
+#endif
 static void __osPackEepReadData(u8 address);
 
 s32 osEepromRead(OSMesgQueue* mq, u8 address, u8* buffer) {
@@ -31,9 +33,12 @@ s32 osEepromRead(OSMesgQueue* mq, u8 address, u8* buffer) {
                 if (address >= EEP16K_MAXBLOCKS) {
                     // not technically possible
                     ret = CONT_RANGE_ERROR;
-                } else {
+                }
+#if BUILD_VERSION >= VERSION_L
+                else {
                     __osEepromRead16K = 1;
                 }
+#endif
                 break;
             default:
                 ret = CONT_NO_RESPONSE_ERROR;
diff --git a/src/io/conteepwrite.c b/src/io/conteepwrite.c
index 5c4f4e2e..ba8210f7 100644
--- a/src/io/conteepwrite.c
+++ b/src/io/conteepwrite.c
@@ -10,7 +10,9 @@ s32 osEepromWrite(OSMesgQueue* mq, u8 address, u8* buffer) {
     u8* ptr = (u8*)&__osEepPifRam.ramarray;
     __OSContEepromFormat eepromformat;
     OSContStatus sdata;
+#if BUILD_VERSION > VERSION_K
     u8 temp[8];
+#endif
 
     __osSiGetAccess();
     ret = __osEepStatus(mq, &sdata);
@@ -28,12 +30,15 @@ s32 osEepromWrite(OSMesgQueue* mq, u8 address, u8* buffer) {
                 if (address >= EEP16K_MAXBLOCKS) {
                     // not technically possible
                     ret = CONT_RANGE_ERROR;
-                } else if (__osEepromRead16K) {
+                }
+#if BUILD_VERSION >= VERSION_L
+                else if (__osEepromRead16K) {
                     __osEepromRead16K = 0;
                     __osSiRelAccess();
                     osEepromRead(mq, (address ^ 1), temp);
                     __osSiGetAccess();
                 }
+#endif
                 break;
             default:
                 ret = CONT_NO_RESPONSE_ERROR;