['ol Pinion head]

Paul, just ck'ed my housing racks.

The pic you are showing, there are the pronounced "lugs" at 8 & 4 o'clock, that is a telltale that you have an 8.5. With 10 bolt cover, appears to be 8.5.

However, of the 3 cast versions of the '71-72 A-body housing, two of them lack these "lugs".

Examining the plug weld areas on each side of the center housing.

Most common '71-72 8.5 A-body hsg:
-2 plug welds outside of each side of the rear cover
-hsg has the two large lugs
-rear cover has cut-outs
A-9 housing ends

Least common '71-72 8.5 A-body hsgs:
-NO large lugs at 8 & 4 o'clock. What protrusions are there, are smaller & cupped, similar to the same casting area on some 8.2's, & all factory Chevy 12 bolts.
-One plug weld outside of each side of the rear cover. One hole on each side right inside cover for grease to flow through.
-ROUND rear cover. Using the cutout rear cover exposes the inner passage holes.
-A9 or A10 hsg ends.


-One version of the bolt-in axle '73-77 A-body rear uses a center cast housing, similiar to what you are showing above.

-One plug weld hole on each side
-Uses cutout rear cover
-As a '73+ A-body rear, the upper spring perchs are spread wider apart, the spring locaters are directly on top of the axle tubes, the lwr control arm brackets have inboard shocks. Last, rear is wider than previous A-body rears.

///EDITTED/ Which brackets are on this housing. What chassis car is it in? ///

If early A-body, you have ANOTHER less common version of the '71-72 8.5 A-body housing. That said, I'm betting you have another style of 8.5 r/e.