The "double hump" heads (casting number 3991492 and 3990462) are equipped with screw-n studs and do not need any machine work. All they need are the correct screw in studs that will accept full roller rocker arms.
I thought those were the heads you were referring to when you wrote "double hump" heads. .
Last edited by MouseFink; 01-31-2013 at 12:41 PM.