Gatorback does sell the plates individually. You can find the different options for GM vehicles here, https://www.sharptruck.com/truck-hardware-gatorback-chevy-gmc-replacement-plate
There are custom fit flaps for that truck. The easiest way to use this link, https://www.sharptruck.com/search?q=gcr31f
Any of the single rear wheel set will fit.
The flaps would fit on the Super Duty. The flaps that go on the F-150 are 23" long on the front and the rear. On the Super Duty normally the fronts are 23" long and the rear flaps 26" long. The 23" long flaps will still work, you will just get less tire coverage.
Here are the two part numbers for the brackets:
Front: https://www.sharptruck.com/truck-hardware-gb759841
Rear: https://www.sharptruck.com/truck-hardware-gb759842
Yes, if you go here, https://www.sharptruck.com/truck-hardware-logo-mud-flaps enter in a 2021 Ram 1500 classic and the site will show you all of the sets that fit.
here are the custom fit flaps you need for your vehicle.
Front: https://www.sharptruck.com/truck-hardware-gcaa768086
Rear: https://www.sharptruck.com/truck-hardware-gcaa770594
They do install without drilling into the body of the vehicle.