Mike, if I understand your question correctly, you are asking if there were different length axles utilized during the 1971 - 1973 production period.
If so, yes there was a difference in the length of the right axles utilizing 28 splines on Mustangs built through December 15, 1972. Specifically, the follow applies.
For the 28 spline axles:
Right axles used through 12-15-1972 were 31 7/8 inches long
Right axles used after 12-15-1972 were 31 25/32 inches long
Left axles were the same length 27 13/16 inches long
For the 31 spline axles:
Right axles were 31 25/32 inches long
Left axles were 27 13/16 inches long
GREAT question!
Source: Hollander Interchange Manual.
BT
