Presume this is the '83 300D. I had similar clunking on my '85. We replaced the guide rod mounts and LCA bushings. We took the springs out because my local shop said one was broken (It wasn't!). Put in new springs anyway. No noise after doing this. The guide rod mounts and LCA bushings may seem OK, but no way to really know until you take things apart.

Front end noise on my R107 turned out to subframe mount bolts that needed re- torqueing. However, this showed up mainly when making slow turns.

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Graham
85 300D,72 350SL, 98 E320, Outback 2.5