Identifying 73 and up disc brakes

str12-340 said

So if that were the only 2 choices, we'd be golden, but there are all sorts of threads here showing folks how to use various disc brake set ups on A-bodies (different body lines, more modern Mopar disc set ups). I'm trying to confirm positively that's what a previous owner installed...

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If you really need to get that "picky" take apart all the parts, lay them all down.
Take some clear pictures of the spindles, and the dust shields, and i can tell you if they did come off a 73-76 A body car, or some other, by the casting design of the spindles, and the shape, stamping, of the holes in the dust shields.
Some differences in the designs between body styles, but they all work, interchange, so don't loose any sleep over it.