I think there is an option package that comes with rim blow wheel, remote mirror, some fancier trim, etc.
In 1971 that option package had the same rim blow wheel as the E-bodies have. And from my journeys many times those cars with that package have disk brakes and 8 3/4 rear ends for some reason. In 71 and 72 you see even /6 cars with 8 3/4's whereas that is real uncommon for a 68 or 69 A-body.
I wonder if your 70 Swinger has the HD brakes that I think come with 14x5.5" rims instead of 14x5" Not so sure about that though.
