My used Yukon came with stock front suspension and cleared BFG 33" tires fine. I have a 2" leveling kit on it, and they still cleared fine, but rubbed when I added Husky mudflaps.
I have two sets of wheels/tires, and neither are GM factory, and they both seem to work fine, offset-wise.
34" tires miiiiiight fit in there on flat ground, but once you start hitting bumps in the corners, or flexing hard, you'll probably rub without some bodywork persuasion with some shears and a heavy thumb-detector.
Question: Why 34" tires vs. 33"?