If you are looking to retain the value of the car itself, a 390 probably would do that the best, or maybe even the Cleveland. That would be iffy though as they wouldn't be numbers matching anyway. But from a HP per buck standpoint the 460 would get my vote. Stroker kits are pretty reasonable to get you into that 500+ CI range, but even in 30 over configuration these are monsters. Doesn't take a whole lot of mods to make them a lot of fun to drive.

Don