I did that exact samething to my Tahoe to fit marginally larger tires on it. You are limited to how much adjustment you can get based on the available threads on the bolts.
I did the search for you:
http://www.elcova.com/groupee/forums?a=tpc&s=2826088551&f=6706011751&m=939607467 3
If you have the air suspension you do not have to be concerned about the rear. It will self adjust.
Black Lingenfelter Lux