Headshot, I read were you think that the Cd on you Dodge pickup to be around .5. NOT EVEN CLOSE! Your truck is not a brick, it's two bricks! A short one setting on top of a long one. The Cd for the bottom may be some place below 1.0 because of its length but the cab, being so short probably has a Cd above 1 and combined you have a brick! It is not the shape of the front of the car it is the shape of the back that counts most.
Paul Van Valkenburgh has a good discription of finding the Cd via the cost down method in his book "Race Car Engineering and Mechnics".
Saw a recent Myth Busters where they drove two identical pickups down the highway until they ran dry with one following the other. It was a long ways on a full tank, over 300 miles if I remember right.
Anyway the test was to see if the tailgate was down if you got better mileage. Well the one with the tailgate up went quite a bit further.
They said, I don't know if it is true or not, that the newer pickups are designed so that with the tailgate up it makes a bubble of air circulate back forward to the cab and up the back of the cab which then tumbles in a circular motion that stops the air going over the top of the cab from getting sucked in behind the cab thus streamlining the air flow (Some of the F1 cars use diverted air to help with the airflow around the open wheels and I've considered experiment with that later on my lakester if it ever actually runs.).
Hope you understand what I was trying to explain
. I think they even put Styrofoam balls or something in the back to see how the air really was circulating and it followed the above statement.
Disclaimer: All of the above could be true or a myth since I saw the show a couple weeks ago and at least 1/2 of those memory cells are no longer with me
c ya, Sum