Well I had those Zeons on my 09 2wd. No need for the level but it did rub the swap bar near lock with no spacers. On my 13 4x4 I have a 285/60R20 duratrac which Was the set i went with after the zeons. They fit with or without a level and no spacers on the wheels. I know that with my 2" level I could easily go up to a 285/65. I am guessing it would probably fit but it would since I have seen 275/65's in stock trucks without a level but I can't say for sure.
2014 Black Express, 4.5" Maxtrac lift, Ballistic Razorback's 20x9, 35x12.5 Federal Cougaria MT's, DeeZee tailgate assist, K&N drop in filter, magnaflow 16" welded in, Diablo Trinity, 20% tint on the front and 5% on the rear glass, AVS Smoked Aeroskin, HID 3000k fogs, 6000k HID's in the projectors.