I had a problem similar to this about 20 years ago. The problem ended up being that one of the alignment dowles was in the block a little to far. The chamfer on the pin combined with the chamfer on the bellhousing allowed the case to move around and not properly locate.

Allan G.

1970 Challenger w/572 Hemi street car and my pride and joy. 1986 T-Type with 272 Stage 2 Buick V6 engine - True 8 second street car. Just updated the engine and put down 928 HP @ 35# boost to the ground on chasis dyno. 1976 Cee Bee Avenger Jet Boat - 460 Ford powered.