Just stumbled across Ralf Kühl's workshop in Germany that specializes in W114 and W115 service, parts and restoration.
It's a very informative site after running it through Google Translate.
Particularly interesting are the photographs of his parts stash and the story of how he acquired and restored a Celette frame straightening machine.
Treffpunkt Strichacht - Angebote rund um den Mercedes Strich 8: Startseite