Three areas to look at before messing with the springs.

Rear differential mount - slight change in height but mostly noticed when changing from fwd to reverse.
Subframe mounts - slightly more change in height but not much.
Trailing arm bushings - definite change in height if they are worn as much as mine were. Hard to tell how bad they are until they are unbolted and lowered. New ones, wow what a difference! From what you describe as tire wear, I would definitely be looking at these!

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Sam

84 300SD 350K+ miles ( Blue Belle )