Pete, Shouldn't be any big problems, those old buicks are good motors. If you don't mind a little costomizing you could use a NV4500 out of a '92-'97? 3/4 or 1 ton Chevy 2wd. Great tranny!! I put one in my '76 behind a 520 ft lbs 454 and it works great! It's a 5 spd w/ O/D. Go for it!!