Update...
Installed front grill block (from rear of grill)
rear tire spats/air dam
vented front wheel wells (needs to be wider based on splatter pattern of dirt)
sealed off rear bumper (where air flow comes off the bed and into the bumper)
details & pics can be found here...
Aero Mods... - Dodge Cummins Diesel Forum
Road trip Saturday, 700+ miles. Best my truck has done on this trip (and all time) is a 23.00x mpg doing reduced speeds, holding throttle steady up hills and coasting in neutral down hills. I had taller tires on back then, 34" vs 33" now. Gonna see if I can break that 23.00x record.