I have an old set of Pro Parts, partial fender-well headers that we refinished and had powder coated. I'm running them with RPM heads, with head studs and we had to modify the flanges a bit to get them to clear the head studs. But, they actually fit fairly good. Yes, the tube length vary quite a bit, but with a blower on 496" I'm not to worried about a few horsepower. The holes in the fender-wells are pretty small, and you barely notice them. Other than hanging a little low, I like the fitment.
I'm manual steering, and manual rack with an Alterkation, FYI.