New Sierra Denali HD 2500 - upsizing stock tires/wheels?

Or you can just slap some 20s on it and not worry about a thing. If the tire you want/get rubs at steering lock then either trim a little plastic or level the front by cranking the torsion keys a bit or getting new torsion keys.
The mph difference in 1-2" taller tire will not require you to reprogram anything but you'll be going a few mph faster than indicated on the speedo at hiway speeds.
Truck will run fine, tow fine, handle fine. May lose minor fuel mileage going to the grapplers. Like 1/2 mpg.