I've heard that a change to a better transmission (possibly with a vac amplifier) was done by 85. I really don't know if that's true but maybe someone who knows for sure will chime in. That would be a considerable plus. Ball joints are easy BTW, I can't believe how I dreaded doing the job when it was so easy. Look for structural rust underneath in the frame, all around wheel wells, behind headlights, where front sway bar goes through body, floorboards, at bottom of trunk, inside trunk under rear window, bumper mounts, under door trim. Check for excessive blowby at idle.

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'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.