I am looking at the new level 8 on the gold suburban on EP. Or, I may buy a set of corrroded 6 spoke gmc wheels and blast and powdercoat them. I do that as my work, so I can do it easy. I think that would look pretty cool too!
255/85/16 i have a 05 2500 HD work truck, the 255 are a 33x10ish, I put them on stock rims. I cranked the bars in the front for about a 1.5in lift, the rear i used airbags. The tires gave me the most lift. The narrow tred pattern does not slow you down as much as a wider tire.
I'm not very familiar with full size trucks but I would imagine your best bet for clearance/effectiveness would be to crank your t bars then swap your old worn out leafs for 3 quarter ton leafs and move up to a 33"(maybe bigger if they'll fit) Tire, should gain around 1.5-2" from the suspension alone and get much better payload with those leafs and raised axle with the tires
If your springs are worn I'd replace anyway. But as far as putting larger tires on without doing a lift.....Cut-out fender flares. Bushwacker makes them for your truck.
Can I recomend looking into what BDS suspension has to offer. They have lift kits at reasonable prices and the best garantee in the bussiness. Cheers, chilli..