Yessir!!!
An air dam is a good start, especially since the truck is more than likely "dirty" aerowise underneath. I use lawn edging material from Wal-Mart on my vehicle. Works like a charm
Anything, no matter how insignificant it seems, you do to help out aero on a rig such as that will be ubberly beneficial.
If you feel more smitten, I would look at deleting the front mudflaps and making wheelwell and rear wheel coverings.
Kammback can come later
