While the Cummins is a great engine the early mechanical ones were loud for sure. The Duramax has always been probably the most quiet, civilized diesel of the 3. Fords 6.0 and 6.4 I would avoid. The new 6.7 seems to be a winner.
You're on the right track with the 3500 truck. Anything less doesn't make sense for a TC. With a SRW you may need to look into 19.5" rims and tires to support the weight. They don't work as well for airing down, however.
My preference would be for a GM truck. I've had nothing but excellent service from my Chevys. My work truck is an '03 F-350 and everything from the engine to the seat belt just doesn't seem as good. But, it does get the job done; usually.
