newbie here, with those heads you can order a rotating kit from eagle to handle 500-600hp for 1400. the part number is b18021l this kit will let you run pump gas if the cam is right. that kit comes in std all the way to .100 over bore....like mr maccarty said a good roller cam would do you good. for 500hp a rpm air gap will work and a 4150 holly 750. cam spec somewere around .550-575 lift those heads crap out around there. duration hi 240-50 at .050 should do well. just make sure you spend a little to have a pro look at the head and set them up for your cam.. don't trust the out of the box heads and just throw them on. i have seen way to many screw ups from ready to run stuff. good luck with it.