I don't know if it was rare or not, but my Uncle had a '72 GMC Camper Special that had those toolboxes in the bed. They were at the bottom of the bed, just below the side trim and forward of the rear wheel opening. It also had 2 extra gas tanks mounted under the bed, but those were aftermarket.
Since you need a bed nayway, it might be worth seeking one out that has the toolboxes.
