Key Question

I am wanting to add a small lift to my truck. I have a 2002 Sierra and I want to run 285s or 305s on it and maybe stock rims or 15x8s. I had been considering a body lift, but have been looking at this lift:

http://www.roughcountry.com/gm-leveling-lift-kit-283n2.html

I know how to install the lift and realize that some components may wear prematurely because of angle changes, but I would like to know how fast parts would wear. I have heard of people running torsion bars that were maxed out that never replaced a ball joint or steering component. I would also like to know how this lift would affect the ride in the front of the truck and what the purpose of the keys are if the stock keys can be used when the bars are cranked (I have hear it puts the bars at a different angle and it provides a stock-like ride).

If I just did this lift, I would run 285s. I am considering adding a 1.5-2" body lift to the truck and trying to run 305s. If you have any pics, I would appreciate it if they were added to this thread.

Sorry if this has been asked before. I know there are a lot of "what would it look like" threads, but I have done a lot of searching and have been unable to find answers to some of my questions. Also, I have experience lifting trucks, but none with torsion cranks or key lifts.