Hey Pat! I'm not sure what the heads and internals are, I was told that the 402 was stock to the truck and stock components. But some times you don't know unless you tear it down. I did adjust them and they don't hit the covers anymore, it idles really smooth so I don't think I have bent valves. I do think I might have found a weak spring today though, I slid the inner spring up and down with little force while it was installed. Do you know what the specs are on a stock dual spring? (open height, closed height, lb's of force measured)