Well, or you could use IDA Pro.
Edit: Here's some source recovery stories
Some folks recently did source recovery for Super Mario 64:
https://gbatemp.net/threads/super-mario-64-has-been-decompiled.542918/
which apparently didn't take too long because the executable wasn't compiled with optimizations. Visual C++ 5's default release configuration had full optimizations enabled, so just a
wild guess that JK.exe is fully optimized, so it would be a lot more work.
Someone else recently did source recovery for Diablo. Which apparently didn't take too long because Blizzard accidentally shipped a debug executable (no optimizations) and Sony accidentally shipped a file containing debug symbols. There are two different compiled JK.exes and I assume neither of them are debug, otherwise someone would have mentioned it by now. Visual C++ 5.0 and up compiled symbol data into a separate file by default, and either LucasArts knew not to ship it or InstallShield was smart enough to warn you if you tried (I would guess both, I haven't tried InstallShield in about 18 years but I remember it was pretty damn near fool-proof). No help there either.