Quoted:
I've seen my friends loaded up at 25900 GCWR (and he had the weight slip to prove it) - not that I would recommend it. GCWR is more of a manufacturer thing as I understand it - the 'legal' limits are the front & rear axle weights, and the weight on whatever trailer you have. Especially with a bumper pull, its all going to depend on how you load the trailer & how well the trailer brakes work. I've got a '96 3500 that I regularly pull about 10k with, and I have pulled about 15k worth of trailer before (trailer is rated for 18k). Its actually surprising how well it handles it - I would imagine your 2500 would have no problems with 10-12k of trailer weight. Just leave plenty of room for stopping, make sure everything is in 100% perfect shape, and have your brake controller dialed in.
I've seen some retarded pulls as well. A guy borrowed my brother's 1ton, single cab, dually, dodge cummins and pulled 30 round bales of hay from Kentucky to Texas. Average weight of a round bale varies from 700-900lbs depending mostly on moisture content.
Do the math...no matter what way it's cut, that was WAY too much weight to safely tow behind a pickup. But he did it, and even said the Ozarks in Arkansas were no problem (my brother's truck is not stock, much more power).
(for the math challenged, you are looking at a minimum weight of 30,000lbs)