Rear End ID help

[68C10HotRod]

About a year ago, I got a 72 Burb with 400ci/TH400/posi SPID options. Well, I finally got around to working on it this last month. Have been noticing some odd things on the rear end lately.
1) the brake shoes are worn on the outer 1.5" of the 2" shoe - drum also doesn't encapsulate the backing plate either & matching odd wear.
2) DS drum was real gunky so figured the wheel cylinder needs replaced.
3) jacked up & spun 1 wheel forward to see the other side reverse.

Decided to remove the cover to confirm the G80 has been stolen in it's previous life. It only got worse, the gears were marked 3817778 11:41 GM 11-68 3. Think this means it's a 3:73 set from Nov 68 in a 3 series carrier. The 400 should have been 3.07 std I believe. Can anyone confirm this?

PS housing tube says HA 1202 W. Not sure how to decode this. Think the gears & housing are from a 1968 & they just swapped the 6 & 5 lug axles - explains the odd brake pad/drum wear. Same with the drum & it doesn't sit all the way down around the backing plate. Also measured 55.25" from back-to-back plate on the rounded outer edge. Wheel mount surface with drums on was 63.75".

Any info would be appreciated & might help others.