Over the next month or two there should be a flood of old cars that have been donated to charitable organizations - they go to local auction - then to EBay.
I think I see one on EBay now, a rustbucket 1976 300D. You know its going to be bad when the front strut rusts loose.
One key to recognizing these is to ask who's name is on the title.....
If not the seller, then they're trying to "curbstone" the car - which is technically illegal. That means they're trying to sell the car over to you from the previous owner - without ever actually owning the car themselves.
Better to go to these auctions yourself so you can examine the car in person.
Ken300D