In that case, you may want to find a copy of the 2 disc King's Quest 15th Anniversary Collector's Edition (1994) since it includes the dual-language KQ5 French floppy disk release that came out after the CD audio version. It retains the original Roland MT-32 midi tracks instead of recordings like the CD version and added digital audio effects present in the CD version that were never included in the original floppy disk release. The code would be more similar to the CD version at least.
I think I've got a better idea: the Amiga version of KQ5! It's also close to the CD version, and I already did a decompilation of the Amiga version of LSL2.
Also, with a bit of trial and error, I've successfully managed to properly decompile a few things that were previously undecompilable. As a result, KQ4 is now entirely in script code! KQ4:handleEvent and Room78:handleEvent were all that was left. This actually freed up quite a bit of heap space.
I've been similarly successful for LSL3, with rm370:handleEvent and rm340's comedian script. Only room 140's RoomScript is left to be decompiled.
There may be bugs in the newly-decompiled code, but at least it's much more serviceable now.