The little 289 in my car have the stock heads and I want to upgrade the heads ASAP. My biggest question is can I go with a 2.02/1.60 valve size and not hit the stock flat top piston? I don't want to be forced to buy new pistons to accommodate as that would mean an entire rebuild (one of those "while I’m doing this" type of things. Or would anyone suggest a 1.90/1.60 valve like the performer rpm head?