318 heads

There's just too many variables

Daily driver/hot street machine/street strip ?
Gearing and stall how far your willing to go ?
Is this a rebuild or just bolt on ?

Basically stock heads can get you to 300hp
With a little port work can get you into the 1:1 hp per cid fully ported can get you over 400 hp.

If your looking for a relatively cheap heads the will flow decent and give a CR bump a set of EQ'S would work.