Jeff, in the last picture of the rear frame rail area, it certainly looks like the two vertical bolts next to each other are painted? do you agree or is this some artifact of the way the picture was taken.
if those bolts are painted how can this make sense? the bracket associated with those bolts seem to be natural...
This picture
If so the two exhaust bracket bolts and nuts are not painted - its nor unusual for the under carriage paint to fade away at the end fo the car before the valance on many examples so that there would be no overspray to get on the top of the car or the one that was following. You can see that the paint on the frame rail is very light. In fact so thin after all theses years (likely was a little heavier originally) you can make out the galvanized frame rail and burns from the spot welds