I've done a few mods like a grille block and modifying OEM parts. The largest contributor is adjusting my own driving habits. The ScanGauge helps a lot! Any real-time feedback on fuel economy will help you figure out how to get the most out of any situation.
Aerodynamics are going to be difficult to modify on the Beast, as it's a work vehicle so it has to be able to take a beating. I may try bolting a sheet of Plexiglas to the bottom pan, and see if shielding the underbody helps.
