i have those heads on my 466.i spent 50 hours massaging them into shape.the nice thing about these heads is that they are easy to port.the exhaust does need work .there is a big hump in the center which can come down.these heads really breath when ported.the secret is to barrel hog um for the biggest valves and then blend in your grind back to the gasket where you scibe and gasket match.on the short side of the runner ,there is lots of room to get some diggin to make them longer and not such a sharp turn.you will know a dove head not just from there casting numbers but the big fat short old style tapered not washered spark plugs. they are a quench styled head with a 75cc chamber wwhich can be polished as well. you dont have to mill these heads to make compression,only if they are warped.the walls in the head between the water jackets have lots of meat and you can port pretty huge.the only thing is,they sure swallow fuel ,but like they are supposed to.