I know you have your heart set on a Dodge but before buying one check out the 2011 Hurt Locker test at mrtrailer.com and a similar test of 1-tons done by Car and Driver in April of this year.
I bought a 2011 Chevy diesel but with a heavy 5th-wheel trailer I would also be looking at the Ford F-450 trucks. Both Ford and Chevy diesel trucks have been a lot more reliable than Dodge and get better mileage. With Ford one has a lot more options to get factory suspension modifications for heavy hauling and towing.
