When I went out to buy a diesel truck to tow my fifth wheel I had it rated Ford first, GMC second with the Dodge rated a never every going to own a Chrysler product but I owed it to myself to look closely at all three. I came home with an '06 Dodge 3500 and have been very happy with it. I'd have to second the other person who said an '06 or early '06 Ram with the 5.9 Cummins. Of the 5.9 Cummins equipped Dodges, the '06 and '07 transmissions were the best. I've got 120,000 miles on it now, including 27,000 towing a 14,500# fifth wheel from Florida to Alaska and back, with not a problem.
I came close to a Duramax Allison GMC and think I would have been plenty happy with that truck also. Two big pluses in the Dodges favor, (at least with the 5.9), engine very easy to work on. Look under the hood of both. You can't hardly stick your hand into the engine compartment of the GMC, with the Dodge, wide open spaces. I installed my own gauges, exhaust brake and over sized transmission pan, plus do all my own maintenance. It's all very easy access. Plus the Dodge has a shorter wheel base making it a bit more maneuverable for a daily driver, but giving you less space in the back seat. Plus, the Dodge's tow ratings are not nearly as high as the GMC.
I may be partial to the Dodge now, but I don't think you can go wrong with either.
