I was running 275/70r18 KO2's on my 2014 with 1.75" strut spacers from readylift and had 0 rubbing.
275/70R18 translation is (275mm * 0.7 aspect * 2 (top & bottom) * 1 in / 25.4 mm) + 18 in for rim size. Come out to a total of 33.16" total height. You should be good with anything under 33.4" height and 285 width.
Ya, that is with the 1.5" installed already. The picture is with the 265/65. I'm going with 275/70 just for the extra clearance; almost did 275/65's myself.
How did this turn out for you? I have had a vibration since ~2k miles, and now have ~28k miles on my truck. New tires are in the near future so I am hoping that I will be able to fix the issue with a simple swap out. Looking forward to hearing if you were able to take care of this.
I have a set of the 4" chrome bars from my double cab if you are still looking. Still in the GM manufacturer packaging, the dealer wouldn't let me leave without them. $350 + Shipping. Let me know