I'd agree that $500-1500 would be a good range without getting more details on the car. If the car was in MINT, showroom condition (looks new, smells new
), then it might be worth more.
Condition is everything on an old car, so rust would limit the value of a pinto. Location is another factor in the value, as a rust-free pinto would be more on the east coast then on the west coast (where rust-free cars in general are more plentiful).