How to make Horsepower?

Thank you very much. It has got a 7 1/4'' rearend with 3.23 gears. I'm thinking i will have the heads milled out(intake,exhaust), bigger cam, offy dual 1bbl intake, and headers. I am gonna see what that does for me and if it doesn't come good enough for me then maybe a 340 will be put in.