My motor went 9's in a lighter car, that's not theory, it happened. Its making more power than it did back then, but is in a heavier chassis now.

Are they the best head for the $, no. I was the first to say that, but, they aren't total boat anchors either. I've been shopping around for a better 59 degree head to replace mine, but I don't think it's economical to switch.

FWIW my car has been 129 and change at 3575+, you can make your own power assumptions.