I've got a '71 220D that I use as my daily driver. I think its been a great car . . . real, real slow. But you get used to it. I think the car would have to be in awesome shape to be worth $3000, and with the rust spots you described I doubt that. I paid $1750 for mine, about 6 years ago. It had 90K actual miles, but the engine was a factory rebuild at 60K. It had no rus, everything worked, even the original Becker!

Eric

1971 220D 133,000
1981 300D Work in Progress