A few other comments on MPG.
First of all, everyone else is right...the words "fuel economy" are not in the Bronco dictionary.
However, to maximize your truck's MPG do as the other posts mentioned - full tune up. In addition, check to make sure your tires are in good shape and are properly inflated. Finally, make sure you go easy on the throttle when accellerating from a stop light: lightening up on the pedal may take you two or three extra seconds to clear an intersection, but if you are not in a hurry at the time then why not? Plus, it can easily give you an extra one or two MPG, especially if you live in an area with a lot of stop signs/lights.
For reference, I have a low-milage, pretty much stock '95 w/ a 351 and I keep her happy with regular maintnance, and the best I have gotten on a long, flat stretch of Interstate in Louisiana was a hair over 15 mpg. And I think I had a tailwind most of the way! The fact is, in normal everyday driving I get about 12 to 13 MPG. I am going to add a high-flow intake and exhaust when I got home and that may help a bit, but I am not expecting miracles. I knew what I was getting into when I decided to buy a Bronco (just about everyone in my family has owned one at some point).