So i'm changing my duster to large bolt pattern in the rear and my problem is in the rear brake department now, I've talked to charrlie about re drilling my drums but per his advice, i've decided to do a brake swap from a B body car. I'll be using the backing plates, drums etc. brake parts from a B body now my problem is has anyone done this? and if so what do I tell Moser to make for my axles. I need the measurements for an A body axle into the housing and b body ends on the axles right?

Kev

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Just call Moser, they make an axle for that swap. They used to keep them in stock.

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Official Cookie and Mater Tormentor.

When I performed the SBP to BBP swap on my Darts, I found complete axle assemblies from 73 through 76 cars, with disk brakes (both were 75s in my case). I've found these in 7¼ and 8¼ sizes.
When I measured one of the BBP against the SBP, I found that the axle housing tube lengths were different. To accommodate this, the backing plate on the BBP axle was offset to the inside a bit. Spring perch offsets were the same, so no worries on that score.

One of the problems I have seen with 73-76 year A-bodies is that rear end gear ratios are impossibly high. The nice thing about the 7¼ is that earlier year cars had lower gear ratios which can be transplanted in with the usual mess that goes along with changing the gear out.
Over the years I have found a couple of 7¼ axles with SG diffs.

The 8¼ has some aftermarket support. Richmond Gear has 3.55:1 and higher (numerically) ratios. IIRC, these gears will not work unless the installed gear is 2.56:1 or higher (numerically). 2.21 and 2.45 gear axle assemblies will not work.

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You can't fix stupid. - Ron White

I hope you have some clearance to the outside of the tire. The A-body axles are shorter from the bearing to the axle flange than the big bolt pattern axles so the big pattern axles stick out of the axle housing farther. Doctor Diff can also get you axles and may save you money over Mosier.

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Joshua

OK here's the deal. Kev has an "A" 8 3/4 spb rear. He wants large bolt pattern. Originally he wanted to get big bolt pattern axles, and redrill his drums. I suggested not a good idea. It is very hard to find the 10 inch 1 3/4 inch brake drums. I suggested if getting aftermarket axles, anyway, to use the bigger brakes, and have the axles made for that setup. I should have a couple of rears that have large bolt pattern 10 or 11 inch brakes, that I can let him have. Either 8 3/4 or 8 1/4.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

Unless something has changed when I went through this exercise years back...

I second Josh on this. The aftermarket "off the shelf" axles that go into a A body 8 3/4 to convert to BBP use the B body bearing > flange offset, forcing you to use the B body brakes. A body BBP brakes aren't an option here. Essentially they are just a shorter B Body axle. Sounds like that's not a big deal since it seems you already have the B body brakes.

Consequently this also moves the wheels out something like 1/2-3/4" I believe. In your duster wheel well this shouldn't be a problem. When I did this in my 71 Duster I was able to get in 225/60/15's with those cheap Cragar $40ish 15x7 wheels from summit. 4.5" backspace.

Another vote for Doctor Diff - axles sourced from him were cheaper and may give you more of a break if you get one of his disc kits.

Side note: if you don't already have the "new" brakes consider doing a rear disc setup. After you factor in the price of hardware/shoes and drums if needed you may be half way to a disc setup.

Side note 2: You can get "custom" axles made for this setup that use the A body offset so you can use the A body brakes. This way the wheel is put in the same spot. I don't recall how much these were but they were significantly more.