OK, quick expedition to the driveway, with a flashlight and inspection of said "mystery brackets", appears to reinforce the first guess.
They appear to be the vertical support brackets for a Snow Plow Installation. So I believe the mystery has been solved.
~C
View attachment 118699 I recently installed a Ranch Hand grille guard on my 2012 Ram 2500, CTD. The grille guard installed where the factory tow hooks bolt. I had to remove the two brackets (shown in the top of the photo) that were bolted on the bottom of the frame rails. What are these brackets used for? The actual tow hooks are re-installed on the inside of the grille guard uprights.