Hi Site……If you shave .080 inches from your P90 head, you’ll have to jack up the cam towers .080 inches too. You use the early 280 valves which are approximately .080 inches longer. With this set up, you don’t need the shorter valve seals……they are used when the L24 head uses a cam with .460 or more lift which would squash those seals. If you decide to do that, let me know and I’ll put you in touch with Eiji at Datsun Spirit…..he has everything you need to build that head. He has a ton of Isky Stage III cams also. If you just send him your head, he’ll build you a piece of art. Nice buy for $25.00.