When I had my '03 H2, I installed the fabtech 6" kit. It was an excellent product but unfortunately along with a liftkit went bigger tires, different gears and supercharger.
Too much for my daily driver...
Having said that, last week I picked up an '06 SUT. I installed the torsion keys and raised the truck up 2 1/2". With a 2" taller tire, that raised the truck up an add'l 1".
3 - 3 1/2" inches was perfect for what I was looking to accomplish. Here's a pic of before and after.
The best part is the ride.... virtually unchanged.
Mark