I had a 02 Z71 Tahoe that I had put ford keys and 2 inch spacers in the rear. I was running 285/70/17 BFG M/T's. It was a pretty capeable truck. Here is a site you might want to check out, their is alot of info on Tahoes on here.
http://z71tahoe-suburban.com/iboard/index.php?&CODE=00
Here is...
Get some Ford keys or some after market keys for the front. Pretty simple process. New blocks for the rear (3" ones). Remove the factory blocks and replace w/the 3" blocks. New Bilstien 5100 shocks on all 4 corners...