Milling Intake Manifold

More work, but milling the intake side of the heads would allow you to use the heads anywhere else. If you mill the intake, then those two would never be good anywhere else. The intake couldn't be used on a different set of heads is what I'm saying. There are formulas out there to do what you're asking. The more experienced members will be along to help you. Until then, try and be patient. Tough to do I know! LOL