Hey, these diagrams are good info. Can you provide links to any diagrams specific for a 1980 300CD. Mine has developed a couple bugs that I can't put my finger on.
Symptom: engine cut off fails intermittently. When the key is turned off, sometimes it works and sometimes it doesn't. An oddity discovered is that if you open the driver's door for about 10 seconds or so before you turn off the key, it works fine every time. If you turn off the key before the door is opened and it fails to shut off, opening the door will usually cause it to shut off before you can get out. How is opening the driver's door connected to the engine cut off operation??
Also could use diagrams showing the layout of the vacuum system that operates the A/C controls in the dash and the center vent flap system as well as the vacuum bleed and modulator system for the transmission. Mine is the earlier four bolt pan tranny used in the late 70s and early 80, phased out in the 1980 model year.

Surflaunch