I finally drilled and tapped the heads for exhaust mounting studs. They appear, at first glance, to be too long, but I've never seen a Shovel up close that had this done, so I don't know. If they are too long, I'll remove them and insert studs of proper length.
Starting the tap:
Keep it oiled! I didn't use much oil on the first one, so it was a bit hard to cut. I applied it very liberally the second time and it cut like butter.
Starting the helicoil in the hole on its insertion tool: