The formular for a BBC chevy is for every .010 milled of the deck surface of the head .007 has to be milled of the intake face of the head or face of the intake manifold.
For a SBC for every .010 milled of the deck surface of the head .0123 has to come off the intake face of the head or the face of the intake manifold.
If we machine a set of heads we all ways correction cut the intake side of the heads so you can buy any intake out of the box and bolt it on.
BBC ends of the intake to be milled off per .010 is .0193
SBC ends of the intake to be milled off per .010 is ..0173
Also if I know whats being done to the heads I will cut the top of the block so the intake does not have to be cut.