Not that it helps much but it might give you a price comparison.
I sold my '72 C20 Custom Deluxe last year for $2800. It had a 402 Big Block and ran perfect and had 130k original miles. It needed paint and a couple of other things, but it did have alum wheels and decent tires and a Leer shell.
I probably could have held out for more, but I needed the cash for another project and the truck didn't work well for my family of 4 anymore. Kinda sucks, since it was pretty much the same truck my dad had that we used to go to the river in during the '70's. My brother and I loved riding in the back, especially over the whoops to Martinez. Things are different these days.