Not to hijack the thread, but on the subject of after market heads. what are guys doing for pre 72 340s with positive deck pistons? Most of the heads I see have closed chambers and the pistons would not clear. I thought a nice aluminum head that flows well would be better than working over one of my sets of X heads.
I'm pretty sure that is the difference on the ProMAXX 63 and 65 CC heads. The 65 have a little more room for the positive height pistons. I think the Edelbrock do the same, hence the 340 version?
