NHT is the option code for the "Max Trailering Package". If you go to the Silverado or Sierra Build and Price, you will find this option in the package groups. It includes a few things, but not listed is a bit stiffer springs and higher GVWR. -13 it forced you to get the 6.2L, but 2014 offers NHT with 5.3L and 6.2L.
Still, all this research and maybe effort to order or locate something you'll spend $30-$40k on just to be right at the GVWR/payload. Eh, just get the 3/4 ton. If you want the new GM truck interior, wait 6 months for the 2015 HD.