Not to go against what has been posted already the Merc W123 series is a car owners like to keep on the road if possible so parting out the car and posting it as such on a Mercedes board may be a better option.
Have a look at:
PeachParts - Mercedes Parts & Tech Info as a starting point.
In my limited experience Carigs lists . ebay and the like are populated by people wanting either everything for nothing or close to it or people wanting this but not that - timewasters in other words.
Tread carefully.
Peter.