I wanted a little more jump off the line, and more "go" through the gears, and this 4.10 upgrade did the trick. My 06 GT feels more alive. Yes you do see a few more RPM's at cruising speed, but I didn't really notice a difference in fuel economy. Not a job for an inexperienced mechanic, but a relatively cheap & easy job for a good shop. While you've got the "pumpkin" open you should replace bearings, gaskets, etc as well. I rebuilt my LSD with a carbon fiber disk kit while everything was apart, and I topped it off with a new girdle for some more strength (and it looks great too!) Don't fear the gear, and you'll be thrilled with the results.