driveshaft angles

33IMP said

I think he is referring to the factory setting. Mopar welded the spring pads at a nose-down 5° angle, to account for the angle of the front segment of the leaf springs.

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The angle of perch on an a-body is angled down, if you set the perch level it 5 degrees UP, in other words its 5 degrees different,
see picture with the line from front to back spring attachments. That’s the angle the housing perch is welded at so the housing-pinion is parallel to drive shaft at rest. When at rest the spring is not arched but designed to be flat when going down the road