I am currently running 305/70-18 (35") Dick Cepek FC II on my Dodge Lifted 6" with the Hemi - so far havent had an issue with what I have towed with them
They are Load Range E - 10 ply
I have also had the Nitto Mud Grapplers in 35 x 12.5 x 20 and have towed a 21 foot boat or car trailers - only issue I have ever had was when it was wet and when applied the brakes it made my truck slide since the trailer didnt have brakes - this will be the first travel trailer to tow with my present setup
The less sidewall you can go with - the better the ride IMHO and also like stated above the Load Range and the Ply will make a diffrence as well - which being a tech I would think you have already factored that in.
2011 Rockwood Mini Lite 2306 - Matt
2004 Dodge Ram 1500 Qaud Cab 4x4 with 35" tires and 3.92 gears, Dynatech Longtube Headers & Fabtech 6" lift + Superchips with shift Tuning
Nights Camped 2011 (37) - 2012 (16)-2013 (2) -2014 (5) -2015(0)
USMC 91 - 95 - F/A-18 Aviation Ordnance