Anyone changed their rear end for more towing capacity?

I think you should evaluate your expectations in changing from a 3.08 to a 3.42.

3.42 / 3.08 ~= 1.11

Tow ratings aside, this means that at any given speed, the 3.42 will put 11% more torque to the wheels and turn 11% higher RPM.

11% is not much of a change IMO. Unless you're having trouble launching from a stop, I'd keep the 3.08 and try downshifting a gear in the transmission. That'll give you a much bigger increase in wheel torque, and best-of-all, it's free.

-- Rob