I have the same truck... but mine came with 265/75/16's from the dealer. I upgraded them to 285's and got an unofficial increase in RAWR to 7500 lbs, which I'm nowhere close to in actual numbers. Our fiver tongue weight is only around 2000lbs wet and loaded.
For tire brands (all in AT's), I've had Yokohama, which are nice tires, but too soft. I've had Hankook DynaPro ATM's which were very good tires - lasted a long time, but which I thought were noisy - however, I found out later that all or most of the noise was a bad hub bearing in the front left that I replaced shortly after I got new tires (and still heard a lot of noise). So I'm sure they weren't as noisy as I thought they were. Now the truck's as quiet as it's ever been.
I now have BFG AT KO2's, and they are just as good as the Hankooks. The Hankooks and BFG's I would recommend, they give a solid ride when aired up while towing without hardly any sway to speak of. The Yokohama's seemed to have a lot of flex when towing, and gave an uneasy feeling.
I also have Bilstein shocks that helped improve the stability while towing as well. I highly recommend Bilsteins.
Good luck!
2010 Keystone Cougar 324RLB
2005 GMC 2500HD Duramax/Allison 4x4 Crew Cab S/B
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