Cutting the deck would be fine. Many will tell you that you have to cut the intake side as well, but I've never found that need. Me personally, I wouldn't do hardened seats and all to stock 318 heads. Too many out there with hardened seats already. 318 heads are next to free. Actually, you can buy remanufactured 318 heads from like o'reilly's for 265 each. Pick something like 1975 so you'll have hardened seats.
