It would be really difficult to determine what would be the proper price for this car. Since its from 1985, if it still exist today, it must mean that it must have been maintained well. But in this things, we just could never assume. You must determine the used car value to determine its price. Know its history. If it has many damage/repair/crash history, the car value normally goes down, and so does the price for it. If it is properly maintained, no crash, all are original parts, and if there are upgrades, the car values either increases or stays the same, also goes with the price. I suggest that you search cars classifieds or any free car advertising to locate a car with the same model and compare which would give you the best car value and pricing.