Yes, you can find all the cars a particular part is used on. I didn't know how to do this until just now. But MB updates/changes there part numbers occasionally, so it is not a fool-proof method as it might miss virtually identical parts (but with different part numbers).

There is a part number for the 3 piece prop shaft on the 123, and each piece has their own part number. So I guess I can look up a few options if interested. What specifically would be most helpful?

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1968 220D, w115, /8, OM615, Automatic transmission.
My 1987 300TD wagon was sold and my 2003 W210 E320 wagon was totaled (sheds tear).