I have a post about TV selection, and I still plan to purchase a heavier TV at some point. That being said, I am toying with the idea of picking up a travel trailer in the neighborhood of 4730 UVW/68...
Before you did ANY mods I would really consider going back to the GMC dealer and getting some numbers on trading for a Yukon XL with the NHT trailering package.
You get the HD cooling package, 3.42 rear axle ratio, IBC etc.
You may be able to do this for very little difference on your Payment and have a really good towing platform.
You can change the rear axle ratio on your truck now but you will risk the warranty. But that may be a minor consideration for you.