Being sure that it has not had material removed before I have removed .200. To be safe if you want to go max you should measure the thickness between the water jacket and the head gasket surface. The other measurement would be the stroke of the rocker arm to make sure the valve will not strike the piston. Not all heads for them were cast exactly alike. You need to inspect and measure all aspects of the head your using before planning your modifications. I just scrapped a head because of water jacket core shift. That is something you will not find until you break thru.