I've got an '07 Dodge with the last of the 5.9 Cummins. The only real concern I have about the truck is the ball joints. They're a known weakpoint of the Rams,but they also have a medium duty diesel engine sitting on them. The Cummins is about 1200lbs of cast iron. The balljoints shouldn't be an issue,but they are. There are aftermarket replacements that will outlast the truck though.

Both the Dmax and whatever Ford decides to use that year are light duty engines. You ever wonder why Ford offers the Cummins in their F650 and up?

In the span of 8 model years,Ford has used 4 different engines. In '03 you could still get the 7.3,as well as the 6.0
From '04 through '07 you could get the 6.0. From '08 through '10 you could get the 6.4,and in '11 you'll get Fords in house 6.7. Not really confidence inspiring.

The Cummins also has the flattest torque curve of any of the diesels. It makes peak torque at 1600rpm and stays within 10-15ft-lbs of peak torque all the way to 2800 rpm. Essentially, at any speed you're running down the road, the Cummins is making peak torque.

The Dodge trannys since '03 are pretty bulletproof...unless you need to run 100hp over stock. The 48RE that was behind the 5.9 actually has fewer TSBs and recalls than the "mighty" Allison. The 68RE thats behind the new 6.7 has proven to be very reliable as well. Dodge transmissions are a non concern anymore. The 68RE has double O/D and the factory exhaust brake is awesome. The exhaust brake blows the grade braking of the Allison out of the water.

Dodge has always been the red headed step child in the truck marketplace. They've come a LONG ways the last 8-10 years.