I had about 650 miles on my tires at 40 psi. I have less than 50 miles on them since going up to 50 psi. Ironically, they seem to ride a little smoother with the added psi. Could have something to do with the stiffer sidewall of an LT tire over P tire. Maybe now it's actually riding on air instead of the sidewall. If you know what I mean.
I do have more room for more tire. I know people have put 33 inch tires on without issue, but your going for a 34 inch tire. It may fit but I can't say for sure. May need to do a little trimming. Good luck buddy
Got my truck last week after ordering it in April. It's an LTZ Z71 Midnight Edition with the 6.2. Here's a list of what it's got for accessories.
GM OEM Sierra All Terrain Wheels refinished to gloss black powdercoat.
BFG All Terrain KO2 285/55/r20
ReadyLift 2 1/4 inch level kit
Bak Revolver X2 tonneau cover
GM Borla exhaust with black chrome tips (both behind rear tire)
Black GM running boards
Chevy Bowtie Mudflaps
Next will be to tint the front windows.
Last pic is next to my brothers 2008 Denali