Hey, Twerp - welcome to the forum.
Awesome avatar.
Definitely, definitely get a ScanGauge. It'll pay for itself in no time with the amount of fuel you'll be saving. If the price seems steep, I like to remind people that you could always use it for 6 months to fine tune your driving and then sell it later and get most of your money back. There's no shortage of people looking to buy these. (But I bet you won't be selling it once you get your hands on one.)
If I had a truck I was using for commuting, that'd be step one, followed immediately by driving adjustments. Have you browsed the
list of driving tactics?
As well, I'd be looking into aero mods - particularly partial grille block and an aero cap. (I'll assume you've checked out the aero forum).
Can't fault Daox's advice about keeping your eyes open for a cheap, small beater, too.
It'll be interesting to see where you go with this.