I don't think you'll get much out of it with those heads. my buddy just built his 383 and tried to do a little trick work to his fairly stock heads. I think he did more damage than good. It was his first heads to attempt. He tried doing some combustion chamber work. Anyway he put his poorly worked heads on a $$$$$$$block and it is slow. Only running 12.8 or 13. With some better heads you can get more out of your money you spent on the block.