hmm, the clunking might be a lot of different things.
axleshafts, driveshaft or differential, on one occasion a gearbox.
on a w114 with sort of the same issue as you describe it was the differential,
Montefeller’s w114 280CE – 3.69 to 3.07 differential swap | Mercedes-Benz turbo
the thread has video of both diff mounted and play found without dissembling anything, aswell as the second video of what was the issue. Seen that on multiple differentials.
https://www.youtube.com/watch?v=5W3629vkI5k
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daily: w123 om602turbo 5speed 200whp, w115 240d 3.07 differential
mbturbo.com turbo diesels+gassers in oldtimers/classics