Need some help controlling body roll

I just got photos of the drum. I never even checked if it was big bolt or small bolt. I am pretty sure it is a b body rear myself now. I screwed up the measurement. I went to the inside of each drum and came up with 53 inches and 5/8.

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I'm really beginning to think that's not a B-body rear, it's too wide.

Those are 11" drums so you have the 5x4.5" pattern. Do you know if they're 11x2.5" shoes or 11x2"?

Your measurement from the inside of the drums is misleading. BBP backing plates are offset by about 1.75" to the inside from the end of the housing. If you use 53-5/8" and add 3.5 you get 57.125" which would be housing end to end, which is no where near a B-body rear axle. That's a tough measurement though because of all the dents and features on the back of the backing plates.

Your other measurement of 3" from the spring to the inner sidewall of the tire is telling. If you take that 3", add the 4.5" backspacing, and the tire overhang on the rim which should be .6" by the manufacturers tire specs you get 8.1", which is wheel mount to spring. If you take a 65-69 C-body rear axle drum to drum it's 61.75". Subtract the perch distance of 43", divide by 2, and subtract half the width of the perch and you get 8.125" for the wheel mount to spring distance.

I'm thinking that may be a C-body rear axle.

When I first saw your photos I thought that's not an a body 8 3/4, those shakels look like offset shakles with one side on backwards, you have a 318 car probably did not come with a 8 3/4.

Here is a photo of an A Body 8 3/4
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My guess is whoever swapped the rear in had to use the shakles to make up for the perch being in the wrong place and raise the rear as others had said to allow the tires to clear.

The shackles aren't offset. The spring is completely in line with the hanger. The aftermarket extended shackles are just weird with that bend. If they were offset in the same direction they could be offset, but they're opposing so the centerline is the same.

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