I wish that I could help, but I'm not very savvy on the NNBS trucks. The thing with 34.5s is that basically anything 34.5 and larger can be looped into the 35" tire category. I am almost 100% sure that with a 2" that you would more than likely get some rub on the front, but again...I'm not certain. Toss a question up in the forums and I'm sure you'll get a better answer as there are a bunch of folks out there win NNBS trucks.
the 275/65s are about the same width as the stock tires...but are almost 3" larger in diameter. I think 33s would be the best fit here, AND you shouldn't need to regear your axles with 33s.
SO i've determined you have about 100 times more experience with lifted trucks than i do. I had a 96 dodge ram before i got my 08 chevy and it sat pretty high already.. I have the 08 LTZ 5.3 4x4 I don't want to lift it too much because i'm not a serious off-road enthusiest.. (I just don't want to get stuck when responding to fire calls in my town) ... I only planned on a 2" tuff country suspension lift (spacers in the front add-a-leafs in the rear) i figure 33's would be a good tire to go with but what about 34.5's? I wanted toyo M/T's but can't get them in 33's without being too wide... stock tires are p275/55/R20 do you think LT275/65/R20 E10's would fit with just a 2" lift?