I just bought a 2004 Silverado 3500 with dual rear wheels and a dump body, with a posted GVW of 12,000 lbs. My question is: how much can I weight it down with breaking it or abusing it too much? Here in NC we can weigh whatever the license tag permits. One dealer told me 18,000 lbs would be a practical limit, while another one recommended a max of 15,000 lbs. I'm a newbie, have never had anything larger than a small pickup, and would appreciate any answers and advice you can give.