B. Body rear end

[J walk]

There is a 8 3/4 for sale an hour and a half away from me.  I believe it is from a b body due to the 44" spring perches.  The seller says it is 60" flange to flange but said that was axle face when I questioned him.  It's to far away for me to go measure for myself so I thought I could get a little direction from folks here.  He believes it is 71-74 but I'm thinking 70. 
  I have a dr. Diff relocate kit and new perches for my rear end and thought this would make it an easier swap as the perches (44") would not need to be moved.  My diff is currently broke and have not opened it up yet but it is a sure grip with tallish gears if I remember correctly.  I believe the bearing on the input shaft is bad.
  This other rear end seems to be reasonably priced with 3:91 gears.  I am thinking about picking it up but am wondering if it is worth the trouble.  Is the e body rear wider then 60" axle face to face?  This could gain me some room in the wells conceivably.  Will my sure grip accept the 3:91's on my center section?  Will my center section fit the other housing and axles?
  Your thoughts and concerns.
  Here is a link to the rear end.
https://nh.craigslist.org/pts/d/gilmanton-iron-works-mopar-classic-rear/7390155874.html

[MoparLeo]

Click on this link for all rear end dimensions
http://www.moparts.org/Tech/Archive/axle/16.html

[HP2]

From Moparts:
Axle flange to flange
B BODY
'65-'67= 59 1/2"
'68-'70= 60 1/8"
'71-'74= 63"
'71-'73 wagon= 64 3/8"
E BODY
'70-'74= 61 5/8"

Housing flange to flange
B BODY
'65-'67= 54 1/4"
'68-'70= 54 15/16"
'71-'74= 57 7/8"
'71-'73 wagon= 59 7/16"
E BODY
'70-'74= 56 31/64"

So it sounds like it might be a 68-70 B body. In my experience, moving the springs in 1" per side with the Dr Diff kit allows a B body rear to bolt right in to an E body.  However, relocating the springs and spring pads with an E body rear housing similarly allows larger wheels/tires, but alters the wheel backspace requirement compared to a B body. All depends on how you want to get there and if you  already have wheels or not.

[J walk]

Thanks Tony, that is the info I could not find.  I was just about to pull my wheels and drums off to measure mine.  Looks like I could gain 3/4" per side of relative back space which is huge.  I have my wheels 15x10 5.5 bs but was waiting to relocate the leafs before buying tires.  I figure a b body could give me the wiggle room to better center a tire.  I am ok with small spacers so this might work out for me. 
  I didn't want to drive 3 hours round trip for something that won't work for me.

[rikkitik]

 I have the Dr Diff kit installed on an E body rear axle. I went with 6.5 BS wheels. As with most cars, the rear in mine is not "centered" to the body.
On the "tight" (pass side) side, 6.5 BS is just about perfectly centered in the wheel well. I doubt you will need spacers on a B with 5.5 BS, as the B rear will move the BS number .75 inch compared to the E rear.
Though you say you already have your wheels, for others that might go this route, the B rear definitely gives more wheel options. Not a lot of wheels are available out to 6.5 BS. Though Weldcraft can modify aluminum wheels, common 8" 4.5 BS +2" = 10" 6.5 BS. Stockton wheel can do steel wheels, though neither is cheap $225/$250 per wheel.

[HP2]

5.5 backspace with the 68-70 rear should work out as the ideal combination. The 65-67 housing only use 5" and E bodies housings need 6", if I recall correctly.

I once entertained the idea of putting a 71-73 wagon housing in the rear and converting to longer, fabricated front control arms. This would have required wheels with 7.5" backspace and produced late model type scrub radius and return to center specs with less roll center migration through the range of motion while allowing me to use later model wheel designs.  I decided the money spent on that would be better spent fixing sheet metal.

[Cratos]

I went with an A body rear and  the 1 inch relocation kit and have 295-50-15s on 15 x 10 keystone klassics fit great.

[GrandpaKevin]

I used a 67 B body rear with Dr. Diff's offset kit under the wife's 71 R/T.

Trimming is needed on the rear valance to clear the offset rear spring shackles.

15x10 wheel with 5.75" back spacing.

Using a 325/50-15 tire best centered and fit was using a 3/4" spacer.

I was leary of getting caught in the rain on drag radials so I went back to 275/60-15 street tire on the sames wheels and spacers, pic below.

325/50-15 install pics at
https://forum.e-bodies.org/wheels-tires-brakes-suspension-and-steering/12/final-15x10-tirewheel-test-with-66-67-b-body-rear-end/12912/