I'm going off of memory here, but I (think I) recall reading something in Jp magazine that said YJ transfer cases won't work in a TJ. It had something to do with the exact angle the case sits at when it is mounted in the vehicle.
My fleet: 91 Miata, 98 Wrangler Sport
, 01 Suburban 8.1L, 14 Impreza, 80 Grand Prix LJ
Jeep mods: 4" longarm + 1" BL, 35" KM2s, 4.56s with dual ARBs... and lots of scratched armor