they will stick out further than mine...I have eagle alloy 187s with 4.5". I had to trim some off the front bumper and not run mudflaps to make everything fit without rubbing. You might get more rubbing than I did...dont know how much difference .5" of backspacing will make. I also have a GMC. Here are a couple pics of my truck with the cognito UCAs and torsions cranked w/ 1.5" blocks in the back. Doublecheck the backspace on them..MOST 16x8s are 4.5" BS.
pics without the torsions cranked:


pics without the torsions cranked:


