1984 300DT: Clunk heard when turning off engine
 

The engine shocks are for reducing the diesel shutdown kick, I would check those didn't become disconnected.

There are flats on the engine shock that needs to be held when removing the nut. I think it's 8mm and requires an open end wrench.

I had the clunk and changing the mounts fixed it.
My old mounts didn't look that bad, but when compared to the new ones you could see the old ones were flattened out some. I think it was the heat shield on the drivers side mount that was hitting the frame on shutdown.

The Motor Mounts look squashed to me or it is the camera angle.

Also when the Motor Mounts get squashed the Power Steering Belt sometimes cuts one of the Oil Cooler Hoses.

The Motor Mounts you get from the Dealer for a 1984 300D are made by Phoenix. Lemforder sells the Phoenix Mounts with the Mercedes part number ground off of the rubber they are made in Turkey.

The Transmission Mount works with the Motor Mounts and can look OK but if it has been soaked in Oil it can turn soft.