as you got into 66 in CA, 68 Federally, and onwards into the 70s, distributor curves and timing specs got more and more "smoggy" and less and less "performance." If anyone has ever replaced your distributor with a parts store "rebuilt," it could likely as not have a "more of a smog" advance in it. Rebuilders are not known for being "correct."
If it has a bit hotter cam, it needs a different setup
And, as I said, the original may not be working optimally, either
