"Mid 60s baracuda 8 1/4"

^^^^^^^He's right about the widths etc., but i may add to it that the first year for the 8 1/4 rear end was in 1969 in a B-Body.
The A-Body 8 1/4 rear end started in the 1973 model year and all 8 1/4 rear ends were big bolt pattern.
It obviously was transplanted into the car sometime after it was built.