A quick way to accomplish the bolt not turning in the hole would have been to grind off five of the six corners on the bolt head and then mill/drill/grind/carve a spot on the hole for that last corner to drop into. The bolt is now keyed in to the hole and can't turn while tightening, but just drops in and out like a normal bolt. No extra hardware required and faster than drilling/tapping for a set screw.