Good luck on getting your Hummer.
I've done a lot of mods to mine, if you haven't already seen my post about building a 4x4 rather than buying a 4x4, you can find my mods here!
http://www.elcovaforums.com/forums/s...ad.php?t=39293
I just need to decided about the front locker, I've heard the diff is not really that strong, and I've also increased the power of my H3 so worried I will smashed the diff, I've also put 35" tyres on which provides a lot more traction and with the raise I've put on mine 3" to 4" the angle of the CV joints are such that I could also start breaking them.
I use mine mainly off road and the reason I want to put a front locker on is to try and control the power a bit more as the traction control on the front really isn't designed for off road, you get this grab and let go action which cause's bouncing at the front end and this is what happens when all the power is unleashed and not controlled correctly.
http://www.youtube.com/watch?v=JYFrd1flwg8