The crowns were over .300 at the reliefs so theres pleanty of room to cut. Minimum thickness according to speed pro is .180, I still have over .220. I'm running .579 lift with 2.14/1.88 valves so the radial clearance was really tight. Had to unshroud the cylinder walls to clear the exhaust valves also. If you build what you're talking about you won't be dissapointed. Just watch where you "cut corners"