Looking more closely at your attachment I’d say the pickups didn’t get a rear bumper. The part number listed is for a 3805 (1 ton panel) or a 3807 (1 ton canopy express).
My thought is those would be what you’ll want to add to the pickup but the brackets will be the hard part- making sure the bumper sits at the proper height as our 1ton trucks sit taller.


1951 GMC 250 Open Express
1968 C10 Suburban
1971 C20 Pickup

My Dad told me "Son, never hit a man in anger- unless you're certain you can get away with it"