Just installed a 1967 B body rear in the wife's R/T Challenger last fall with Dr. Diff's 1" offset bolt in kit.
Here's some info:
All B body leaf spring perches are 44" apart
The 1966-67 B body rear is the narrowest that will be a direct bolt in but are difficult to find.
The housing is 54 1/4" flange to flange
1968-70 B body rear ends are much more common and will also work great but is just a wee bit wider at 54 15/16" flange to flange.
FYI your current E body rear is 56 31/64" flange to flange and the perches are 46" apart.
-B body 8 3/4 housings show up often on E-bay.
-Keep checking your local Craigslist, B body 8 3/4 rear ends show up often around my area.
-A local Mopar swap meet might have some too.
*Take a tape measure and make sure whatever rear end your looking at is correct.
If buying off the internet I would just try to find and buy a bare B body housing as it would be cheaper to ship.
I suggest you buy brand new(stronger) axles with pressed on bearings from Dr. Diff.
You can re-use your Challenger's current rear brake setup.
The rear end install on my wife's R/T was a super easy bolt in deal.
She wanted to keep the car's old school 15x10 rear Centerlines (that have a terrible 3 5/16" back spacing) because that is what her late father put on the car when he restored it in the late 80's.
Tires are 275/60-15.
In the top picture you can see just how far the tires stick out with the stock E-body rear end.
Second and third pictures are with the B body rear end installed with the same rims and tires completely tucked under the car.
