2004 2500HD 6.0ltr towing tune ?'s

[GAMEOVER]

My brother has a 2004 Silverado 4X4 2500 HD with a 6.0ltr and I think it has a 4L80E(not sure)...He wants me to build him a towing tune. Anyone got some pointers on what I should focus on. I'm going to be honest I've never tuned a truck for towing, should I data log with the 28ft Toy Hauler attached or?

Thanks

[LM7Tuner]

Yeah the HD's have 4L80E's usually. I'd data log with the trailer, if you want it to perform ideally with the trailer.

[GAMEOVER]

Yeah thats what I was thinking, First thing I'm going to do is the AutoVE on the truck and then see how it goes...:) Hopefully I can help him with his extremely bad gas mileage and the transmission gear searching when he's towing his toyhauler...