368 & trans ?'s
 

I posted under Deville forum but got only one response. I have a 81 Coupe Deville with a 368 and a th400 trans. I want to put a 700r4 in it. I was told by a seller on ebay that it won't bolt up to the engine. I thought all gm big and small blocks and thier trans interchanged. Please help.