Have You considered swapping out the frame? I just put an 83 olds 88 frame under a 51 foor door,clears the rockers with little trimming, needs to be stretched 2 inches to match the wheel base. We actually took some out as we had a 5 inch gap inthe roof after chopping the top ,so now it's 113 wheel base,leaves lots of room for any rear sump engine,we stuck in a 472 cadillac. Hank