I measured the truck as it sits. 20" is my starting point on both the side skirts and front air dam. I must say, DAM! that is high.
I can get maybe 1.6" with a tire change, and I could get another 0.75" by lowering it as much a I dare. There is only 2.25" to the bump stop now, so a drastic lowering would be just that, drastic.
The tire change is interesting, it is 7% too fast now and probably optimized for 70+ freeway speeds. When I tow I go 60 or less. Reducing tire diameter should help and not hurt economy. Buying tires hurts economy big time though.
__________________
2007 Dodge Ram 3500 SRW 4x4 with 6MT
2003 TDI Beetle
2002 TDI Beetle
currently parked - 1996 Dodge 2500 Cummins Turbodiesel
Custom cab, auto, 3.55 gears