heads, because that 360 is going to have dished pistons and the 360 is in need of any compression bump it can get. Many will tell you that you have to cut the intake as well, but I've not had to and I've done it more than once.
If take .040 off the heads, and later replace pistons with flat tops, will the the valves still clear the heads with a .450 lift cam or would I be upgrading heads at the same time?
