The new 6.6 gas I'm pretty sure only has 3.73 gearing, not option for the 4.10.
I was waiting on the 6.6gas to come out, but after reading about it, I held off. The towing reviews have not been great, and it seems they have alot of torque management on it.
I've decided to go with a Ford, their new 7.3gas seems to be a beast, and it has a 10 speed. TFL did a tow test with both trucks, and the Ford blew the Chevy away. On the same road the Chevy got down to 40mph with 14k lbs, and the Ford held the speed limit of 60mph with 16k lbs, and still had pedal left.
I've been driving a Chevy for 20 years, and was really disappointed with what I've seen of the 6.6 gas. I think if they had put an 8-10spd trans that could handle the power and not have to limit the power, and offered 4.10's it would be a great truck, but GM messed up.