Good grief guys. It's right here...
An accurate 8 3/4" rear axle width list
8 3/4" Rear end widths, drum-to-drum:
A-BODY
- '66-'72= 57 1/8” (or 57 13/16” for BBP axles and brakes)
B-BODY
- '62-'63= 58 1/2" (And '64 Max Wedge)
- '64 = 60 7/8" (Exc.Max Wedge)
- '65-'67= 59 1/2"
- '68-'70= 60 1/8"
- '71-'74= 63"
- '71-'73 wagon= 64 3/8"
So, it really depends on which "B-body" rear end you have. And no, it's not like a "3/4" per side, since we can pretty much rule out the 63 or 64 rear end. The narrower 65-67 B-body rear is still 1 3/16" wider
per side than an A-body 8 3/4. And the 68-70 B rear is a full 1.5"
per side wider.
Can you run a B-body 8 3/4 in your Duster/Demon/Dart Sport? Absolutely. I have one in my '74 Duster, and I run 18x10's with 295/40/18's. But I have a 1/2" spring offset, the quarter lips are trimmed back, rolled and pushed, and my 18x10's have a 7" backspace (+38 offset).
So what offset should the OP run? Beats me. I'd need to know which B-body rear axle is in the car, if the springs are in the stock locations or if someone didn't move the B-body spring perches and pushed the spring out reducing clearance. And of course what wheels the OP would actually like to run. But for a ballpark, it's pretty simple. Most Dusters/Demons/Dart Sports with an A-body 8 3/4 run a 15x8 with about 4.5" of backspace. So, if it's a 65-67 B rear you need more like 5 11/16" of backspace, and if it's a 68-70 it should be more like 6" of backspace. Of course, if it's a 71+ B rear all bets are off
