I don't think you will be disappointed with the Cummings engine.. Before my new turbo I installed the 370hp marine injectors and a 4K governor spring kit (running the bosh P7100 mechanical pump on my 12v) the EGTs would go through the roof if not careful.. the bigger turbo really helped with that problem.
I recently drove from MS down to Tarpon Springs, FL with a friend of mine to pick up his new 26ft Glacier Bay - hauled it back at between 70 and 75mph.. He has a two year old Z71 and admitted the other day that he thought he was going to "burn his truck up" trying to keep the Z71 and Glacier bay at about 65mph on the interstate...
If you have not already your should join the TDR and start keeping an eye on the posts there.. Great info and a great bunch of guys..
Best of luck..