4x4 gmc value?

[c20pickup]

the truck in queston is a gmc 4x4. I believe it is a 1969 and a k20 (not sure the year, its not specified, and I cant see wheel lugs in the pictures posted but it has a 205 t case, so that leads me to believe its a k20) the truck is for sale locally for 500$ and the owner doesn't seem to know much about the truck. the ad says the body is shot, the bed Is salvageable. truck has a 307 (oil burner) and a 4 speed, dana 60 rear, 44 front, 205 t case. I was wondering what the running gear and drivetrain is worth under this thing