Plymouth duster rear suspension questions
Best handling geometry for leaf springs is discussed here, it's instructions for setting up leaf spring sliders but it holds true with shackles too.
DoctorDiff kits are a 1/2" offset.
The MoparPerformance offset kits are advertised as 3/4", but they are not. The front spring hanger is only a 1/2" offset, because there's only a 1/2" between the factory hanger and the frame rail. With the MP kit, the rear shackles are offset 3/4", and they tell you to move the perches 3/4" per side. The result is that you side load the spring, still don't get a full 3/4" of offset, and try to force the springs to be narrower at the rear shackles than at the hangers, which is opposite from any angle you want.
I seriously doubt you'll be able to run those like that on the street without rubbing.
Pictures can be deceiving, but it looks like the sidewall bulge is even with, or possibly even outside of the outer lip of the quarters. Not sure what if anything you did to the inner lip, but if that's ride height it doesn't look like you'll have enough clearance to keep those from hitting the quarters with suspension travel. You need a good 1/2" of lateral clearance to the quarter lip to keep stuff from rubbing. If you throw some weight in the trunk and look at what happens to the quarter lip clearance I think you'll find you're going to have issues.
Best handling geometry for leaf springs is discussed here, it's instructions for setting up leaf spring sliders but it holds true with shackles too.
DoctorDiff kits are a 1/2" offset.
The MoparPerformance offset kits are advertised as 3/4", but they are not. The front spring hanger is only a 1/2" offset, because there's only a 1/2" between the factory hanger and the frame rail. With the MP kit, the rear shackles are offset 3/4", and they tell you to move the perches 3/4" per side. The result is that you side load the spring, still don't get a full 3/4" of offset, and try to force the springs to be narrower at the rear shackles than at the hangers, which is opposite from any angle you want.
I seriously doubt you'll be able to run those like that on the street without rubbing.
Pictures can be deceiving, but it looks like the sidewall bulge is even with, or possibly even outside of the outer lip of the quarters. Not sure what if anything you did to the inner lip, but if that's ride height it doesn't look like you'll have enough clearance to keep those from hitting the quarters with suspension travel. You need a good 1/2" of lateral clearance to the quarter lip to keep stuff from rubbing. If you throw some weight in the trunk and look at what happens to the quarter lip clearance I think you'll find you're going to have issues.