[I mis-posted this in another section]

Daughter has a '73 150 6-cyl she got with no rear bumper and no brackets. She ordered this particular bumper:



of which I've seen only one ever on a 150, but I'm no expert. She also bought these brackets:



The long brackets themselves will bolt right up as indicated in the instructions, but the backing plates or short bracket pieces, whatever they are, don't seem to apply here at all.

So, the problem: the transition from the straight bracket arms shown in the kit above to the bumper itself. The bumper mounts to something with three fasteners, and it's that something I'm missing and cannot find anywhere.

Any idea what this added bracket piece is called, what I need to specify--or should I just go to a yard and hope to find them? I doubt it's going to happen.

I expect the needed pieces are roughly triangular in shape with a web that bolts up the arms coming off the frame. Suggestions?