Sierra 3500 SLE has an allison transmission and a duramax diesel.
both are HIGHLY regarded.
but will cost about 38 grand if you get a 4dr 4wd extended cab with diesel, tranny, camper style mirrors, towing package, cruise control and fifth wheel package.
Ford F-350 XL (4wd, 4dr) will set you back about 35 for
extended cab XL, with 6.0 l v8 diesel, 5 speed, ac, cruise/tilt, tow command, class V hitch, heavy service suspension, telescoping mirrors
Ram 3500 ST will set you back about 35 for
quad cab (no crew available), 5.9 L V6 Turbo Diesel, AM/FM radio, folding trailer mirrors, speed control, trailering group, full size spare (i cant believe some of those are options)
im pretty sure i picked the same base options for both im not sure on Ford, or Dodge and dodge you cant get a extended cab.
now as to which i would pick....
the GMC is proven, but slightly more expensive. Ford is all new truck (engine is the same, tranny the same im pretty sure) and the Ford also has 2500 cash back. i didnt notice any for the GMC
the dodge, im not sure about it has a much smaller engine, its a V6, compared to V8.
so pick between Ford, and GMC.
a Chevy, with the same options as the GMC runs about the same price. 38 grand.
so you really have Chevy, GMC, Ford as options.
up to him which he likes best.
MIKE