Where are you (and the car) ?  bob

A car this old will probably sell for no more than $2 - 3k, and probably
only a few hundred if traded in, given its condition. If the body and
interior are a bit beat, then probably the best thing to do is sell it
locally for what you can get.

If you are mechanically inclined, and the car is in otherwise nice
shape, then it might make sense to fix the oil leaks if they only
involve the pan or valve cover gaskets, and replace the radiator with an
aftermarket unit, but I would not invest more than a couple hundred
bucks and an afternoon or two of work to prepare it for sale. If the car
 can make it through your local or state inspection, this is also a
good selling point but again, don't spend too much money to fix it up to
pass inspection.

Donating can make sense if you are already near the threshold for
charitable contributions, and you are in a high tax bracket, but find
out how much you can really write off.

Ebay will give you a national market, but one difficult problem there is
 getting the vehicle to someone several states away, and handling
payment. Make clear how you wish to handle these in your ad if you go
this route, and state its condition honestly, but in the most reassuring
way you can. Get a feel for how similar vehicles are selling before
setting a reserve price. Too high a reserve will scare off potential
buyers, too low will leave you open to a lowball bid if the auction
attracts few qualified buyers.