Nice choice. If I had to drive a truck, that is the exact model I would have chosen. Good start with your airdam, but I have a few suggestions if you ever decide to be more elaborate.
Suggestions- Curve the airdam so it extends from the bumper to the lower control arms while maintaining a smooth radius (or parabola)
- Fabricate wheel splitters and boattails for each of the four tires. Try to keep the taper ~7-10 degrees and radius all corners. The faces directed towards the wheels should be slightly wider then the tires
- Build a full underbody, starting at the front and extending back as time allows
- Build full length side skirts that extend as close to the ground as clearance will allow
- Construct an aeroshell
- Lose the passenger mirror
- Install a grill block
- Build rear wheel skirts
Hopefully these ideas will serve as a brainstorm and guideline if you choose to delve a little deeper into truck aerodynamics. Your car has a ton of potential. In any case, I watch with interest.
- LostCause