A friend of mine has a 327 bolted up to the original torque tube on his '51 3100. It works. It screams at highway speed, but that is what 327 engines like.
Another friend of mine put a 428 Pontiac in a '50 3100. He had to find an old Buick Saginaw pattern bellhousing to mate to the original transmission. He said it worked fine. He did say that he got nervous when he put his foot into it. He said that you could see one side of the bed elevate a bunch from the frame twist.
