I used the car as a car for almost a year before I finally started to get the itch to "fix it".
The first thing I wanted to do was to assess and keep an eye on the rust. Then I wanted to rebuild the front suspension - and of course the back then followed...
...the more I worked on the car the more I was aware that things weren't as good as they could be. The rear subframe bolts for example were totally corroded in place
The mounts were stuck too
Still I got that done
Rear subframe removal and bushing replacement
I did the rear wheel bearings too
W123 rear wheel bearing removal help needed
I got the front and rear suspension rebuilt (quite a common job for many a new W123 owner) and even got it aligned (self alignment)...
How I adjusted the toe in / out, camber and caster on my W123 300D
...I got it back on the road only to find that the engine was kicking out more and more black smoke.
This was the culprit
Broken valve guide
OM617 manifold oil = broken valve guide