Supporting mods are going to be what you want to get lined up first. Then your cylinders will need to be ported for the 4mil (spacer plate shouldn't be thought of) get some custom domes cut for the 4mil. Supporting mods: billet impeller, good clutch, pancake bearing, billet basket, pro-mod trans (when you start making any real power shifting becomes an issue), bearing detent, adjustable timing plate, poly case saver, good reeds, good intakes, big radiator. Etc.