HA is stamped on the rear end indicating its a 3.73 gear ratio (i also verified this on the stamp on the crown gear). Its the original, as far as I can tell, from 1966. I don't think my uncle changed it out to something else. There are 12 bolts in the dif cover (not 10). 8.875 inch ring gear without posi.
Bearing dimensions are:
2.531 OD
1.622 ID
0.832 W
Seal:
2.591 OD
1.62 ID
0.5 W
I have been using this to source parts:
https://www.lmctruck.com/1960-66-che...ferential-1-2t
The original truck is a 1966 GMC C1000. My uncle chopped and shortened the frame and put on a GMC 1960's hood and step side box before he gave it to me back in 85'.
I don't have pics handy but will later tonight when I get home and post them up. Thanks for responding!