The sad part is there is no way to set a price on an old truck. Ive talked with sellers who think they are sitting on gold when its just a rusted out hulk... And Ive also seen very nice shaped trucks go for cheap. The best way is to listen to your gut and try not to let love at first sight blind you! Does it run and drive? Any rust? Title?
Of course if you had any pics we could look at we would definately be able to help more!
Good luck, Jeff