Thanks, all. I'll look into the cost of having the pit bull adapters welded on. They're cheap. If welding cost is reasonable, probably do that. Second choice is XRCajun's drill and tap method, if first choice is too expensive or too much hassle. Third choice is to stick a hunk of JB Weld on the swing arm, let it become semi-hardened, then form it into spools. Should hold no problem. Hmmm. Maybe that should be first choice.
mcromo: Thanks for the offer on the tank pad template. I have one somewhere already -- maybe yours!