[GRN69CHV]

Very possible all they did was a home hone-job and threw some new rings in it. You have to get it apart to know for sure. You m ay need nothing more than a .030 overbore and some new pistons/rings to match. I would not bother changing the heads for the 396. Too many other variables. What is the rest of the setup in the car (gears, trans, converter, headers, exhaust, suspension)? Unlike what a lot of people try to tell you, unless you go with say a 454HO (425HP) motor, you don;t just drop a crate in & go. 502 crates need revised fuel systems and larger exhaust to work right. You need to get some more definitiion first.