Hy kenparker, the only automatic other than the Powerglide that was engineered to bolt up to the six cylinder Chevy is the Hydramatic, that being said any of Chevies automatics can be installed behind the older Chevy six cylinder after you purchase an adapter. Personally I think the 200 4R would be a good choice, but you will get all kinds of suggestions on which transmission to use, hope that helps.