Lucky man, the part # for the rear passenger side air deflector is (drum roll)
M1PZ-5811398-A. This comes with the screw. The two push pin fasteners have to be purchased separately. (AUVECO 20988).
I believe the first tire rotation can be back to front and front to back. Subsequent rotations should be diagonal. Assuming good alignment and tire pressures being maintained.
Truck tread rubber on the interstate tore my right rear off. Didn't notice it for a few days. Went ahead and replaced it. Probably should have removed all of them and saved 37 bucks.