Schumacher headers, grinding boss on block

Here's an idea. You could center punch the outside face of it. The drill like a 3/16 hole in about as far as you think you're going to need to cut. God forbid you go through to the water jacket, BUT, if you do, then all you'd need to do is tap that hole to say 1/8 NPT and put a pipe plug in it. Of course at that point, you'll need to back up and punt on getting the header to fit......maybe heat the tube up in that spot and put a soft dent in it. But I don't think you're going to run into trouble grinding that off.