On my '90 -- and I think they may be the same on the '82 -- there is only one inboard bolt. It hangs down from the body brace, and goes through one of the two holes at the flange where the rear tank strap attaches inboard.
You lift up the tank/skid, and the threaded bolt goes through the skid/strap hole, and you cinch it up with a nut and washer. the inboard rear of the tank/skid "hangs" from this bolt.
1990 Grand Wagoneer with HD towing package -- everything works! (for now...)