I think making a jig or fixture to drill or mill the head to make it fit the block as opposed to modifying the block to make the head fit it, is a good idea as well. Many times there is more material around the bolt bosses in the head to offset the bolt considerably within getting into water. Plus, if you mess up its easier to fix the head than the block. I like how the valve cover fits on an LS style head, it would be real easy to fabbed one, once you got the individual head sections welded together.
