2wd cab to 4x4 frame ?

[72frmtrk]

Has anyone ever put a 2wd cab on a 4x4 frame? I have a 72 chevy 3/4 ton 4x4 and I bought a rust free 67 cab off a 2wd drive truck. I put the cab on the frame and now the transmission bell housing is going to hit the firewall down by the accelerator pedal mount area. For some reason the 2wd drive firewall is alittle different than the 4x4. It looks like if the engine was moved forward everything would work. Should I pull the engine and drill new holes for the engine crossmember to slide it forward? Has anyone else ever done this project before or does this crap just happen to me? I've spent alot of money on this truck trying to make it as new as new can be. Everything has been redone! I'm in the beginning stages of losing my sanity! Can someone please help me?