You might want to consider an F350 DRW truck. It will tow 15,000 up a tree. My trailer goes 17500 and over when everything is on board. I towed for a year and a half with DPF on and climbed all the rockies without a problem. Now there is a trade off with the 350 as you can get a 4.10 rear axle or even a 3.73 and I think the 2009s and 10s had a 3.55 available but maybe not. With the 450 I think all you can get is the 4.88 which is a real fuel eater. So, you give up a little power and gain a little economy with each higher rear axle. Mine is a 4.30 and I got 7.5 to 9 towing. Didn't drive it enough to check non-towing mileage.

In addition to low fuel mileage the primary problem with the DPF technology is diluting the oil with diesel and the extra wear this causes. If you can't delete the mileage is what it is, but there are some things you can do with the DPF on to keep the dilution under control. I was doing OK with an oil management program that went like this: added a quick drain oil spigot. Changed oil and filter at 5000 miles. Between changes at each 1000 miles I would drain the oil down to one quart low and add a quart of fresh. It helped a lot as verified by oil analysis reports and cost $17 each oil change cycle. Hope this helps.