I guess that's a good way to look at it. Thanks. I think I got to the bottom of my bumper question. The issue seems to be what type of bumper one is talking about. On sport bumpers like you showed pics of the brackets are bolted on so the bumper is interchangeable. On step bumpers the brackets are welded on so the bumper would not be interchangeable. At least this is my thinking on the subject.

1965 Chevy C20 Stepside