After nearly 6 years I finally have a rear bumper back on the wagon. The original was damaged at some point in an accident. I found a rear bumper at a junkyard in Great Bend Kansas. See attached video. I bought the bumper from the white 1962 Tempest wagon. Owner has about 2000 vintage vehicles in his yard.
I sanded the back side with 80 grit paper and then painted satin black.
https://www.youtube.com/watch?v=IQ5DjPskOUs