Magnum Head / sunk exhaust valve

Man. Look how wide the intake seat is in the 2nd pix.....wonder if that head ran really hot to do that....

The insert will have a bit wider load bearing area in the head material than the valve will typically ever have. That's all you can count on to keep it from sinking as badly. But how far you can cut things down from where the exhaust side is and not get into the water jacket, IDK.