As 67galax advised, in Swing-Away, Type 1 (78-86); Brackets have sharply angled straight corners to match the older body. 87-96 have smoother curves.
"...The outside tire carrier will swap bewteen year models, although there are slight styling differences for later models. Only a real Bronco guru will notice the difference in the center-plate width and added bracing on later models.
Swing-Away, Type 1 (78-86); "...Brackets have sharply angled straight corners to match the older body. 87-96 have smoother curves..."
All of the carrier use a tailgate support bracket, so if your rear quarters have the holes the tailgate may have been swapped out (likely due to common rust issues). You can install just the inner support bracket for the tailgate and drill holes thru the skin if you really want to use the outside carrier. Just my $0.02, it's a bad design that puts too much stress on the rear quarter panel, even with a stock tire. I've seen many panels get crumpled or damaged from the carrier swinging out too far.."
Source: by our departed friend justshootme84 (Randy Z, Casual Mudder) ... Rest-in-Peace Randy...