A gear swap will likely bring everything back to where it was before the big tires, torque, mpg etc. Adding a tune will only increase the power from there. As I mentioned he is already running the EVO.
He currently has the Edge EVO tuner. If he really wants it, money won't be an issue. Here is a link to a similar thread I started on DP. It has a neat gear calculator someone made in Excel.
http://www.dieselplace.com/forum/showthread.php?t=252115
Works pretty cool.
Buddy of mine just took delivery of his '08 LMM Dually and immediately put 22.5" Big Rig Tires/Wheels on it. He considering going with 4:56 gears to bring back torque to where it should be. Is there a downside to doing this? Will it bring the speedo back (close) to where it should be?