Building a '64 Electra, originally aquipped with a 401 and the 400 transmission, the block and one head is cracked. Have a '62 401 originally equipped with the Dynaflow, and want to use the '62 engine in the '64. Are the mounting surfaces of the two transmissions similiar? Will this swap work?

Not without some work! You will need to swap cranks or have the 64 flexplate machined to fit the larger crank flange surface of the earlier engine. You would also need a bushing for the crank center since the dynaflow has a larger center section that goes inside the crank.

I have just finished this conversation with Carmen Faso. He has the bushing you can put in the crank flange on you 62 motor and he has the flex plates made to fit---then your TH400 will bolt right up. There are some balancing you need to do to the flex plate, but he can go over that with you. You have a good site here with a wealth of people who speak Nailhead. Dr. Frankenbuick steered me to Carmen for a special built pick-up tube I needed and he is a wealth of info and parts fot the Nailheads-----give him a call-------------(716) 693-4090 Good Luck!!!