if cost isnt an object, then no question get the cummins. They simply pull better and more effortlessly. I pull 16klbs in the mountains and it works well. I have the 68 tranny and it works fine, but 16klbs in mountains can use 3.73 gears..which cannot be had on a SRW...even though I ordered my truck last year I am ordering a 2016 dually with aisin for my weight and driving locations.
For your weight a SRW would be fine, but if you ever consider going bigger in the future keep in mind a DRW opens up more doors.
As an aside, I can get about 300 miles per tank towing (10mpg towing the 16k)...towing quads on flat trailers in the mountains I can get about 16.5...buddies with gassers and same weight and same trip get about 9...that equates to quite a bit more stops. Good luck!
