I've owned a 2005 Dodge Ram 2500 with a 5.7L Cummins for 14 years. It's been a tank! The engine is nearly unstoppable and gives me all the power I need. We towed our 12,500lb 5th wheel with it for 10 years and it towed it perfectly, even long steep grades didn't slow it down. We sold the trailer and I put a shell on it and put a mattress in back. I use it for hunting and it has never failed me.
Two things to keep in mind with the Dodge; the transmission and front end. They can be fickle. I replaced the transmission with a heavy duty ATS transmission at 170,000 mi with no problems. The front end can be annoying, just make sure you keep up with the servicing of it and it should give you no big problems.