I run 20's with 3.55 rear and at 70mph I'm turning 1800 rpm in overdrive , still have more than enough zip to go up front and take a look around when I want , were are you coming from with the 3.55 will make it run like a pig.

 

not having a truck like yours i will guess the engine hp would enter in. i would tend to use a lower rear end i.e. 4.1 with a lower horse power engine. and with a higher horsepower i would use a higher rear i.e. 3.55. just a thought.

 

haven't done any towing with mine since i bought it (july '12) but with my 2010 CC hemi 4x4 with the 3.55s and 20's, i get 23mpg at 55mph according to the display. at 75 for 300+ miles i was getting 18mpg. with a mixture of city and hiway driving i average 16mpg(pencil&paper method). i have a diablo programer(91octane tune) and k&n CAI, everything else stock.