It would help those responding to questions if everyone would put enough in their sig to let us know which - 5.3 vs 8.1 - 4x4 vs Z66. Just a thought - it is embarassing to post an answer and then discover that you just advised a 2wd drive guy to put it in 4HI. 
BTW; C1500 is 2wd and K1500 is 4x4
BTW; C1500 is 2wd and K1500 is 4x4