Gary,
Sorry I am late to this thread and this is my take on the 2008 Dodge trucks. They are a very good vehicle if maintained and with some slight changes made to the truck.
I bought new a 2008 Dodge 2500, Mega Cab 6.7L Cummins with the 68RFE Auto 4X4, differentials are 3:73 in Nov 2007. I have 112,000+ miles on this truck and I am pulling a 34RL Cedar Creek 5er for the last 15,000 miles with this truck.
I have modified my truck starting in Dec 07, and still at it, starting with a set of gauges, Boost, EGT's and transmission. I than added a Smarty S67 in Aug 09, with a TBE made for a 2006 extended cab long bed truck from MBRP after several emission issues and recalls for the truck. I did not delete the EGR cooler only blocked the output from the cooler to the air intake and discounted the valve from the system, per Smarty instructions. My mileage went from an average of 12MPG to an average to 15 MPG in town. Pulling mileage went from 9-10 MPG pulling a very light 5fth wheel trailer to 12-13 MPG pulling my Cedar Creek which is 13.5' tall and heavy. The exhaust brake runs constantly and is still the original turbo. This was drilled and cleaned once at 13,000 miles by the Dodge dealer.
I also installed a Mag-Hytec deep dish transmission oil pan with Mag-Hytec differential covers front and rear. These all have extra oil capacity and are Al for cooling benefits. Trans temps when pulling are between 180 and 200F depending on grade. The rear differential is 145F measured by IFR gun at rest stops. These were installed Jan 2009.
I am using a Glacier Diesel Fuel Filter after the primary fuel filter but before the CP3 fuel pump, installed March 2010.
Air bags were installed at April 2011, and a wireless controller was added in 2015. This is only to level the truck so, the driving lights when on don't shine in oncoming driver’s eyes.
The front end was rebuilt at 81,000 miles drag link failed and I had the entire front end rebuilt with grease able ball joints, April 2015.
I changed out my tires and rims on the truck to Nitto Dura Grapplers with a set of Mickey Thompson SideBitter II rims, the tire size is LT285/70R/17 126S, these are for summer use only when towing my 5er. Otherwise I use the stock size tires and rims in the winter.
After our trip this year I had the front seats rebuilt. The driver and passenger seat cushion were replaced with the installer adding spacers to the passenger seat (1.5") raising the seat up and lumber support also for the passenger, this is electrically controlled. They were than covered in leather matching the factory seat colors.
We have enjoyed this truck and I will probably not sell my truck. I am intending on keeping this for another 200,000 miles which means this maybe another 20 years or so. By than I will be too old to pull a trailer and drive the truck anymore. I will be approaching 90 by than and I don't think anyone would want me driving than.