HELP HELP HELP!! Need to Id this BOP rear end.

[Jason14x]

Okay Guys I need some damn help. For 100$ I couldnt resist buying the rear end I found online. We all know above 400 HP the 7,5 is going to explode at some point if you arent careful and smart. That being said I found this 10 bolt B.O.P. rear end. The rear end was in a 1971 Lemans( this is what is making this hard as hell). 1970-1971 was the year GM decided multiple axles from all its divisions was no longer the way to go, so SOME of the 1971 vehicles got the 8.s other the 8.2. The Lemans is one of only a few vehicles that had both and a very rare Nodular rear end.

So to the point....I need help determining for sure what the hell I have? Either way its going in my 87 Aero . I have done all the research, and know about pretty much all the different ways to identify them but with so many variations and possible random rears ends I need some help. I have measured the cover bolts which should be 3 3/4 . Pinion nut, Spider gear bolts...and guess what ...they all dont align!! I will post every identifying mark and picture I possibly can. I took the cover off and the only thing I havent done is pull it totally apart and measure the diff. So I BEG of you someone tell me or help me at least narrow it down. I do know it was the original axle out of the 1971 Lemans , Has the bolt in axles and has tabs that hang down on the bototm of the diff. So here we go.

 

[81Regal]

It sure looks like an 8.2 to me. I have a spare axle out of a 70 Skylark that I can compare casting numbers to.

 

[-dw-]

8.5 has square corners on the bottom of the housing. Unlike the pic.

 

[Jason14x]

Thanks guys. Problem is there are alot of different pictures, comparisons, and what not that all say different things. It's still way better than the chevy 7.5. When I finally pull the axles and pinion I will let you know 100%. It also has a 71 or something on top

 

[DRIVEN]

8.2

 

[Jason14x]

 

[DRIVEN]

The BOP rearends tended to have tall gearing. We had a posi 8.2 with 2.56s out of a LeMans. It had press on bearings like a 9" Ford.

 

[Bonnewagon]

8.2. All my Hollanders says is it is unique to 70, 71-72 Tempest and no others. We could use the late great pontiacgp right now. He had that rear in his '85 GP.

 

[Jason14x]

Thanks everyone. I will be fully disassembling the rear end later today most likely. The support is there for 8.2 at least so I will probably go limited slip , not gonna race it so that should work for me. Other than that any upgrade suggestions from you alliance? I know I will need the different arms any suggestions on who makes the better/best ones ? Upgraded axles? Best gearing ratio for highway cruising..5.3 / 4l60e combo?
Thanks guys/girls

 

[64nailhead]

26” tire and 3.42’s.