Go to this site for a partial answer:

http://www.ridgenet.net/~biesiade/Fordrears.html

Maybe the length (width) of the rear will give you a clue. I note that I do not see the rear that I have on this list (a 1974 Maverick) so the list is not complete. Obviously the ratio is a 2.79:1 rear which apparently was common in the early 1970s when the gas crunch occurred, but I can't answer further.

Don Shillady
Retired Scientist/teen rodder