My brother has a '64 "slab side" that he put a 460/C-6 combo in to tow his race car trailer. The truck is gorgeous and runs 13s ("empty"), while getting around 13 MPG pulling the load. You can see it Oct 13 on MuscleCar TV. They're interviewing my niece because she drives a Maverick "bracket" car. They pitted the Maverick against the pickup for "fun" (running aginast his 9 second Mustang wouldn't be "fair"). He still had to "let up" to keep from beating her in front of the cameras.
I know he put a later front and rear suspension in it. Contact me at:
I'll give you his contact info and you can talk to him about the swap. As far as "gas" engines, hard to argue with 460.