Fair price 71 C10

[CETompkins]

I have a chance to purchase my uncle's 1971 C10 and was wondering what a fair price would be. It is a 71 C/10 ps, pb disc, lwb 2wd, it has been painted once and retains all it's original sheet metal and 98% of everything else. Bumpers and hub caps have been replaced the rest is all original, Engine and trans were rebuilt at 60k but are numbers matching, the truck has 79k original miles on it now and has been garaged since 1980. I only have two pictures to give you an idea how clean this truck is. I would like an idea what I should offer him. I have an idea but would like your input.