I am wondering if you can modify the crossmember on the 65-66 full frame cars to accept a th400? we have a spare crossmember and are wanting to swap a th400 for the st300 in the car now. obviously drive line length will have to be addressed. Bob
My 65 GS Skylark has a ST400. Just move the existing mount cross bar back with some scrap steel 1/8th inch plate (two plates actually, one each side). Bolt one end of the plate to the existing ST300 frame tab location, bolt the crossmember to the trans, mark and drill the new bolt holes on the extension ends. Mine has had this simple mod for years, no problem. Can't remember for sure if the rubber tranny tail shaft mounts are the same but I think they are.
I just made a crossmember from rectangular heavy guage tubing, made it kind of w shaped, it worked fine Doc
