We bought the wife a new (2015) 2500 Big Horn crew cab. 2nd week of ownership we put a flatbed on it for horse trailer pulling and it serves our needs in fine fashion. Road mpg did drop from 15/18ish to 14/16ish with the flatbed and the associated aero change with the flatbed.
The 6.4 is very OK in Arkansas and the Ozark Mts. pulling a 10k horse trailer. It was adequate in the Rockies with 12k worth of trailer on Hwy 160, Wolf Creek Pass and from Pagosa Springs to Montrose thru Ouray Silverton. Over those passes we ran @5,000 rpm in 1st gear for miles. On both sides. But per Chrysler that’s what the 6.4 was designed to do.
66k miles with Penn Ultra 0-40 oil changes when the indicator says time (7k usually) one transmission fluid/filter change and all’s still good. The only time I miss the Cummins is in the Rockies. Also we do like the cheaper gasoline vs diesel. My math just doesn’t show a paybacks for us with diesel.
Good Luck
RonR