We went with a 2007.5 Dodge 6.7L. Had the choice of buying a 2007 Dodge with the 5.9L, both new. Worried about buying a 1st year new engine design but the 6.7L had exhaust brake and a much better 6 speed transmission.
In the first 1 1/2 years my Ram was in the shop more than on the road. The 6.7L's new emission system was very problematic. In that time the turbo was replaced 3 times, several computer upgrades, O2 sensors, heater grid and EGR cleaned etc. Was going to lemon law it but Chrysler offered me a 100K $0 deductible bumper to bumper warranty. I decided to keep it.
In years 2 on all of the engine troubles were gone. Warranty did pay for a few things, A/C failed, electric mirror failed intermittently and one of the trucks computers failed. That was several years ago. I have not had any further issues in 50,000 miles. I think there were 1st year design issues that were all resolved. Today I'm pretty happy with my purchase and would recommend a 2007.5 6.7L Dodge if it has been well maintained and all recalls and emission related TSB's performed. Strong engine that tows extremely well.