The Utiline rear bumper is a hard to find item. Did you post a wanted ad on sweptline.org or just look for one listed? I haven't seen one listed in a long time but someone might have one they are willing to part with.

There are still lots of these trucks in salvage yards but most are long wide bed trucks with big aftermarket bumpers.

A good tailgate, grille and mirror arms are still out there but you'd be better off looking in the South. The tailgates up here are usually rusted through. I bought 2 really nice grilles from local salvage yards. I've bought many mirror arms over the years as well.