Since you're approaching the weight of a semi truck, lol, and going whole hog on a hi zoot brand new Denali, I'm sure you're aware the 2017 models will have another 150ft lbs torque and that LP5 will eat LMLs for breakfast.
Regarding srw vs dually, you're looking at a pin wt north of 4000lbs. Technically you're in dually territory. IMO depends on usage. Few trips a year not a ton of miles. Not xing the country multiple times thru wind rain and the dark of night, truck is a daily driver 300days a year, go srw, put some good tires on it, shore up the springs and roll. (IF you're experienced with big trailers).
Partial,full timer, primary tow pig, lots of towing miles, not so much parallel parking in the city, get the right truck which is a dually.
