It's the #115. 5/16" diameter, end and side cutting bit. Looks like a mill bit. I held the dremel parallel to the crankshaft and just worked the square edge of the bit from the outside edge of the lug working toward the crankcase. It worked very nicely. Easy. Wally World has the bit, too.

I also mounted the engine mount with 6-32 socket heads into blind nuts, easier to shift/change for different thrust/offsets, etc.