I run a set on one of our 512 cars. I purchaced my set complete cnc std. port window. The heads make good power for "what they are". I don't think I'd do it again though. As stated above best bet would be to have a good head builder start on them from bare cores if you decide to use the pro comp. It took a fair amount of work to get mine corrected. It's a good design but Real Eddy Victors would be about the same price when all is said and done.