I can't post the pics, so you'll have to Google them for comparison. But to me, the rear bumper of the 1971 thru 1973 Mustangs look exactly like a Maverick or Comet small rear bumper. I know the valance below might not be the same. But the bumpers themself look like a match. I've seen some older threads where people used the 1970 Mustang bumpers, which look pretty much the same as the 71/72 or 73 bumpers... even though the body style changed. Can anybody confirm that they're the same?? Ford is notorious for dipping into the same parts bin over and over again.
I took a Maverick small rear bumper to Melvin's Classic Ford Parts to compare to the Mustang bumper and they are different.
Ok, so looking at the comparison picture, it looks like the main difference is the bend angle at the end of the bumper. One is more "V" shaped, while the other has more of a "U" shape to it. I'm not sure which bumper is which in the picture. But if the Mav/Comet bumper is the V-shaped one, couldn't you just compress the Mustang bumper a bit with a hydraulic press to make it fit??... or, is the Mustang bumper just wider in overall length?
The Maverick bumper in the above photo is the one that has rust showing (top bumper). The brand new Mustang bumper still wrapped in paper does not have rust (yet). Cometized hit the nail on the head about the Mustang bumper being wider. Best I can remember about 2" or so wider