Racing Head Service makes a couple of dandy cast iron heads, #11301-02 for hydraulic roller with max 0.600" lift or #11301-03 for solid roller with max 0.750" lift. When I do a DynoSim, I always de-rate the flow by 5% just to remove the fluff from the manufacturer's published flow rates. Even with doing that, either of these heads make insane power for a reasonable price. Each of these part numbers is for the 320cc intake runner models.