Actually if he steps up to 35's he's going to want to regear. I ran the stock 3.55 gears on my truck with a 6" lift and 35's for 9 months. Best thing I did for my truck was ot have a set of Yukon 4.56's installed. Regained all that lost power and no more constant gear searching going up hills. Plus since he's in a 2WD it'll actually only cost him half of that, about $700.

 

im gonna argue with you, its not a necessity like your making it sound, you also have the 5.4 i have the 4.6 tuned, intake, exhaust and i have no troubles even when towing over a 1,000 pounds. never really towed much more than that. if you decide you need more power do a tune and if your still unhappy regear. my trucks faster than it was stock i believe.

heres a video of my 4.6 vs erics 4.6 same mods but i have 35's he has OEM size tires. i got a slight early start my brakes didn't stick from the sand in them (we were at the beach) and at the end i let off. usually i catch back up after he shifts as i dont shift for another 15 mph. that was up to about 85 mph i think.
http://www.youtube.com/watch?v=6ux1Uk_Kics

as for gas mileage city i get b/w 10-13 mpg and 13-18 mpg on highway depending how fast i go.

only time i ever wish to regear is when im driving hilly highway, truck shifts not terribly to much but enough to hurt the gas mileage. if you live in the hills then re-gearing i would really recommend and agree with wxscpo