[aerohead]

Since it's a Dodge,you might look at the 2013 Ram 1500 for ideas.This new 1500 has the lowest Cd (0.36) of any production pickup.They do use active,air suspension to lower the truck for highway duty but you might see some cleanup tricks they did.
Having the front airdam as low as your lowest undercarriage components will help shield oncoming air from colliding with those bits and pieces and also all the tire faces.
If you could do rocker panel extensions or 'running boards' as low as the airdam,flush with the outsides of the tires,it would provide a surface to hold the air alongside without turbulence.
And these would net you some of the benefit of a full belly pan.
Closing up all the gaps around the wheels are a source of drag reduction as well as full wheel covers.I realize it doesn't 'fit' the 'image' of a 4X4,but it does cut drag.
Wheel skirts can also be part of your under-body flow management recipe.
Also,cooling and air conditioning air dump into the under body region,so some grille blocking could be part of the drag reducing equation as well.The grille opening on my truck represents only 1/12th of the radiator's surface area.