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