The Hookers have 4 hole flanges on each cylinder flange. They will fit all 390 427 428 configurations that's what makes them nice. No they are not original and take some extra effort to install but your stockers wont be a cake walk either. Good luck on what ever direction you choose.
I guess our biggest concern is that...although yes they have 4 hole flanges, they aren't designed to accommodate offset configurations like the stock 428 heads. Under this setup, two of the upper holes can't be used without additional fabrication. My biggest question is really whether people have continued to install them without modification and only use 2 of the 4 upper holes in offset configurations.
Our assumption is this would compromise proper fitment as two of the flanges wouldn't be fully secured at the top. But, if people have continued in this fashion and not had issues, we are happy to try it.
Hooker does not make a setup from the factory designed for the offset bolt holes unfortunately.