Nate:
Other modifications include Rotella synthetic oil and Moon discs on the wheels. Oh, yeah, I've put lots of stickers on the truck.
I've got fuel consumption records for the last 98,000 miles or so, so will be able to see any changes that might occur. For the sake of the discussion, I get about 22 or so in "around-town" riding, which means the 22 miles of riding at 55 on the way to and from work each day during "summer". Winter (which i define as the six months or so when I've got the winterfront on the truck) I get about 19 mpg. Cross country with no trailer gives about 24-25 mpg, and cross country with the 8 x 16 by 9 1/2' tall trailer yeilds a titch under 15 mpg.
We do not ever exceed posted speed limits, and there are no interstate highways within 150 miles of us, so that means most driving is done at 55 or less.
Oh, yeah -- stock tires are LT245 - 16, and the economy numbers above reflect that size. This past winter I ran 265's and economy dropped about 5% (adjusting for various errors in circumference, of course).
Is that enough to get you started on making an EWAG?