Here are pictures of my rear bumper on my 28AR RPU:

Notice how I extended the repro bracket to get low enough. I welded up the bracket from bar stock. I happened to have a cut off original bracket(the curvey part) to attach the bumpers to.
I also put the LED trailer lights so I could be seen while driving. Not original but I like it and happened to have two extra rear bumpers.
Car is up on my lift with the drivetrain out now to install rebuilt motor, 39 transmission, and Mitchel OD. Just put the 28 plates on as well.