I have been slowly working on this almost since I bought my truck. I dug up several websites about pickup truck aerodynamics and improvements. Here are a few:
A Truck That Drinks Less Than a Car? | Popular Science
http://gcep.stanford.edu/pdfs/ChEHeX...0_11_trans.pdf
Improving Aerodynamics to Boost Fuel Economy
RoadandTrack.com -- Tech Tidbits - Tech Tidbits — September 2004 (9/2004)
I also took a close look at a RAM SRT10 about 2 years ago. Some of the interesting things are the front air dam/bumper cover/splitter, the full tonneau cover w/integrated spoiler (said to improve airflow), lowered 2 inches to cut aero drag, and I noticed the air conditioner condensor and the radiator are inline, not side by side like other RAMs. There is about a six inch space on the driver's side of the radiator that is covered with a piece of black plastic, to cut drag through the grille.
I looked at my wife's 08 Avenger and discovered it has a full belly panel under the engine bay. I have been working toward several of these mods since I got back from Iraq. I will see if I can add the pix to my gallery or garage...
My truck will get over 23 mpg on the highway at 65mph now. I am aiming for 30...
[edit] I also need to ask if there is a how to for measuring Cd via coast down?