F body rear end fit a duster?

Yep, I had one installed in my car when I bought it. Trying to sell it off now, lol. They swapped the whole rear suspension, which doesn't exactly fit because it's the wrong shock style (bayonet end on the axle side that was binding bad on hard bumps), but that way they didn't have to change perches since they kept the iso boxes. They did it the wrong way by just spreading the spring aparts and bolting it all in, but the rear end fits dimensionally pretty well.