If one shaves too much off of one of these heads, You remove the "quench trench". With not enough room for the air to flow when the Big Bang takes place, much heat is created which will turn what is left of the quench trench gun metal, case hardened blue and cooks the intake valves.
I must say that the added compression from doing this results in a remarkable increase in performance, but at the cost of a perfectly good head in short order.
I have heard of angle milling a head, favoring metal removal on the exhaust side of the head. This preserves the quench trench, while increasing compression ratio. Then you will only have to worry about throwing a rod which likes to break where the clamp bolt for the wrist pin is when the engine gets pushed too hard.

1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission