How much it was planed is pretty critical because of the alignment rings. The head and intake have the pockets cut into them only so deep to hold these rings, and excessive milling or planing will make the ring bottom out and hold the flange surface on the intake away from the head keeping it from sealing against the gasket. If it was planed more than .030", it could be very close if not beyond what the limit of the pockets depth is in the intake ports given the much wider machining tolerances of 60 years ago. So if the machine shop inadvertently planed more than needed for good measure, they may have created the issue themselves and not have realized it.
