I will also be replacing the OEM Transforce AT's on my 2500 in the next couple of months... spoke with my tire guy about which brands to consider (he carries many). His first question was how many miles are on the truck and how deep is the tread. When I replied 22,500 miles and 4-6/32", he said I was lucky to have gone that far, as truck tires on a medium duty Diesel powered truck towing a trailer fairly often are usually good for ~20,000 miles. His recommendation was another set of the Firestones, although Cooper, Continental, and Michelin are good, too. We will compare load ratings based on my most recent CAT scale numbers. While I do not need serious off-road capability, something with decent traction (along with load capacity and tread life) will be my choice. The 'stones have (surprisingly) not been all that bad, and are currently still safe, but after my next trip, I will be spending some money on tires.
In the past, I have used Cooper, Conti, and Michelin with no problems, but they were on smaller vehicles.