[hughm]

So a quick update:
I ditched the cattle guard, which probably saved 80 lbs, along with the spare (another 50). I brought the tires to 70 psi (they are 80 psi tires). I couldn't go higher with the pump I was using. Also, these tires are 235/85 r 16, same diameter as factory. I also started pulling in the rear view mirrors on the highway. I have a panoramic rear view inside that allows me to see better than the side mirrors so it's safe. I also removed the cross bars for the luggage rack and had already removed the third row seats. Also changed the air filter.

At first I took the engine computer back to factory settings and noticed an immediate drop in perceived gas mileage on the onboard computer, so I brought it back to the high performance setting is was on. Then took a trip to Austin and back, with about 100 miles around Austin. This was about 85 percent open road driving, 15 percent Austin traffic. When I got home my on board computer registered 25.6 mpg, and I knew it had to be off. I went to fill up (same pump as first time), and my gas mileage registered at 20.8436725 mpg. So now I know I can't rely on my onboard computer. I know I had gotten a high rating before that I matched with the calculator at the pump, but it turns out my son had borrowed and refilled my truck about 4 gallons last time I calculated, so that explains the disparity.

So I'm not getting the mileage I thought I was, but nearly 21 mpg isn't too bad for the minimal stuff I've done so far. My next steps are to block off some of the grill and then start the process of putting on a belly pan. the gargantuan wheel openings really could use some love too, but that will come later.

I expect this to be a slow process. I also have a '50's house I am in the process of insulating/renovating.

Thanks everyone for the good advice.