Based on the following chart I assume you mean the LT Trailboss correct? Since it doesn't appear the Custom Trailboss comes with an 8 speed.
In my case I probably won't consider any of the high priced models (LT TB, LTZ, and High Country). I do not want leather seats which I believe takes the RST off the table (at least I think they are standard with leather seats unless I am mistaken). Since the WT, Custom, and Custom Trailboss aren't offered with 8 speed transmissions I believe the LT would be the best choice for me.
I think in my case I will have to look for an 2wd LT (all-star edition for g80) w/ the 5.3L V8 or the Diesel and in your opinion either with 3.23 should be fine if I wanted to put 35" tires and a lift or just get the Max towing option and have the 3.42?
Thanks for your advice.