The EPC shows the OM 621 starter to fit those models only (no sharing with the 180D). The dealer or MB Classic Center would probably be your best bet. Maybe expensive, but it'll be the right part for certain. Part number is 000-151-86-01.

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'81 MB 300SD, '82 MB 300D Turbo (sold/RIP), '04 Lincoln Town Car Ultimate

Sooner or later every car falls apart, ours does it later!
-German Narrator in a MB Promotion Film about the then brand new W123.