3894860 on housing.
1GM3862691 on ring gear.
14 43 so 3,07:1 open drive.
11 66 on ring gear so Nov 1966.
GA1207G axle tube suffix code.
GA means 3,07 12 bolt.
1307 means December 7th
G means Detroit gear and axle.
56,75" between backing plates.
63,25" wide on mounting surfaces.
This is the first one I have come across in 30 years .
Brackets are for Impala .
I also have an Oldsmobile 12 bolt in another ad.
Email your phone number if you want it.
Pickup in Ridgecrest CA 93555.