You will need to do some research on a value.
Keep in mind However that there will be quite a bit of work to make this car safe and reliable. Fuel system, brakes, lines, hoses, cooling system. Not to mention some over looked items susch as wheel bearings front and rear seals etc. Rusted up suspention parts, tie rods, shocks, age of the tires.
You need to look at the whole picture.
There is always something to do on this type of car.
Time is money.....If this vehicle needs extensive refurbishing there is a lot of time and $$$$$ that adds up.
If some of the service work has recently been preformed you may want to adjust the price acordingly when establishing the value of the vehicle.