I have a 2006 Megacab with the 5.9 diesel and 6-speed manual. At 73,000 miles, no issues, just oil changes and fuel filter changes. I get about 17-21 depending on how I'm driving, and that's with 4.10 gears.

I heard the newer dodges are not to bad. It's a good looking truck, and as long as you don't care about power, rolling coal, or much modification, they will do just fine. If you go Diesel and plan to tow, don't let someone tell you that you HAVE TO HAVE 4.10 gears. I wished I had 3.73 and it would still tow just fine.