Go straight to 3.73 or don't bother the swap. The 3.42 is such a negligible change its not worth the effort. Yes I drove both and yes I have a 3.23 geared double cab with a 6.2.

 

What gearing is in yours?

 

I have an 6.2 with the 8spd and 3.23 4x4 on factory 22's I get 14~17 in heavy stop and go traffic. Any type of trip over 40mi and when the runtime on the engine is over an hour the mpg soars, easy 18~21 and I have seen as high as 29mpg on the 50mi average over a long trip (100+mi). Serious, they are really efficient for how big they are and how much power they have. pretty incredible IMHO,

 

the max tow 3.42s... I wanted the 3.73s, but they didn't offer it with the 8speed.

 

Mine gets 15-17 city and 19-21 hwy with 3.42 max trailer package. Cold air, longtubes, and tune. I have about 6k miles on it and it stays steady at those numbers. I have drove it easy on the hwy but can't get any better than 21. Gets 19 with cruise on