I hope that you guys realize that when you increase your gearing (i.e. go from 2.73 to 4.10) your stock odometer is actually counting mileage faster than you're putting it on, UNLESS you get it all corrected with the install of a speedo gear that is calibrated to your new gear ratio;
for example, lets say that your stock gear mileage was 20 mpg highway- that would be true because everything is in sync with eachother
now change those gears to 4.10 and now your odometer is maybe counting 1.5 miles for every 1 you actually travel, which appears to increase your miles per tank at your next fillup because what used to say 225 miles with stock gears when you got to the pump now says something like 380.
i know i dont post on here a lot, but i was big into jeeps before I got my stang and gearing is a big part of offroading, however the principals remain the same. basically, unless you correct the speedo with a new drive gear, you have to recalculate your MPG to allow for the correction.
i hope im not stepping on toes or making anyone feel like im being a jerk and i also apologize if im stating the obvious for some people, but it just has to be kept in mind if you're looking into doing this swap for the "better" mileage