Re power steering gear boxes, I was just at PickNPull and their Hollander printout shows 1990-85 280CE/E & 300D/TD gear-boxes interchange. Might also be true for manual gear-boxes. Not sure why they don't list 240D. I know 82-85 300SD gear-boxes are different. Of course, doesn't say the Pitman arms interchange. If my 1960's Mopars are a guide, when changing from power to manual gearboxes, one needs a longer steering column rod to reach, so check that. There are after-market adapters (expensive) for Mopars, but wouldn't work for a W123 rod.

I find a gear-box in almost every 300D/TD I see at PickNPull (2 yesterday), but all are as worn as mine, showing 5+ threads on the sector-adjustment screw. That makes ~6 I have looked at in the last few years. I once found one w/ only 1.5 threads showing and thought "great", but thought to adjust it before undertaking the big removal task. After adjusting out play, it had ~6 threads showing, meaning they probably drove it like old movies, toggling steering +/-20 deg on a straight road. Getting tired of pulling together all the tools to hopefully have the enough to pick a gear-box then haul them home unused. P-P sells a rebuilt gear-box for $516.50. Rock doesn't list one. Hopefully, they replace enough hard parts to get the adjustment back. If not, it may have limited life since some part inside these boxes appears to wear in every car.

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1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans