[64-1/2 first.... 66 now]

I'm using the factory ford heads that are ported and polished with pinned rocker studs.

So, you're using self-aligning rocker arms? If stock rockers, have you checked for binding?

 

[64-1/2 first.... 66 now]

I am using stock and stock replacement style rocker arms.

Rail type rocker?

How exactly do you check for binding?

With a wire feeler gauge inserted in the slot between the stud and rocker arm at full lift. Best done with a light valve spring installed.