The better flowing heads should pick up 1.5 to 2 hp per cfm gained. The roller cam could help or not. Twice I have switched from customer picked solid roller to good grind solid flat tappet cam and car went quicker. Also quit breaking rocker arms and shafts and pushrods. If everything that we have bought, that was supposed to make our cars faster, actually did, we would all have 6 second cars.