Heads, cam, intake, headers make the power so you have to pick the parts you are going to use before you can predict the power. 500 hp is easy with a 500 inch shortblock. If you want 600 hp then you should use Trick Flow 240 heads and pick a cam that will hold power a little longer. If you want 700 hp then you need to move up to a MW head like the TF 270 or an Indy EZ head. You'll also need a bigger solid roller cam and a good intake, correct headers and the correct carb.