Is your head right? Other than the drooling, inability to grasp simple concepts, and chronic irritability during the fuel moon, how do I know if my head is standard? Or how much can I mill my head if I don't know its history? Here is a rule of thumb from a knowledgeable Mopar flathead person. Unmolested heads measure 2 inches thick when measured from the flat spot where the head bolt sits to the block to head mating surface excluding the head gasket. So I just measured mine. On my 218 which I believe to be unmodified with the exception of a truing cut measured 1.956 inch. Or .044 short of stock. My milled head on my 56 engine measures 1.939. I had asked for a .050 cut which should be 1.950, so it seems that one had a slight leveling cut also.
So measure twice cut once! Good luck.