Also, the amount you remove is not a linear measurement, but rather an amount relative to the cosign of the angle.

GM BBC 109cc closed chamber head: Head 0.0065" per 1cc
Remove 0.007" from intake side of head (or manifold) per each 0.010" removed from head/block
Remove 0.0193" from end rails on block for each 0.010" removed from head/block

GM BBC 119 Open chamber head: Head 0.005" per 1cc
Remove 0.007" from intake side of head (or manifold) per each 0.010" removed from head/block
Remove 0.0193" from end rails on block for each 0.010" removed from head/block