318 Build on the cheap

With the 302 or magnum heads, 9.5 compression is within reach. With no milling and the good .024" head gaskets you will have right at 9.0. Much higher than that without quench, and you'll have detonation trouble. 9:1 is plenty enough to make good power on pump gas. Just choose the right heads and you will be on your way, even with stock pistons.