My 2008 6.7L, 2500 Ram Mega cab is pulling a 2016 34RL Cedar Creek with no issues. One item I strongly believe is to monitor the engine either with gages and or a gage cluster; such as an Edge Insight. I watch my EGT's and Boost pressure when towing and will shift to 5th gear when the EGT's start to climb above 1100F, boost pressure is kept under 30 PSI at all times. The other parameter I monitor is the transmission sump temperature this is normally under 180F on a 90+F day when towing. But will rise to 200F when backing up the trailer on a slope or in a campground when position my trailer.
My other items I have added for longevity of the trucks operating systems are Mag-Hytec Differential covers, Mag-Hytec transmission deep oil pan, Air bags, a secondary fuel filter, Smarty S67 and LT285/70R17 126R rated tires with Mickey Thompson Side Biter II rims. These are rated to support a load of 3750 LBS at 80 PSI.
2016 34RL CC; 2008 Ram Mega Cab 2500HD, 6.7L, 68RFE 6 speed, 4X4, Smarty S67, 100K+miles