I am in the market for a used 3500 diesel truck to tow a FW. My search is almost entirely online, as these vehicles in my price range are hard to find locally, therefore I am willing to find one 1,000...
Best thing if you are committed to a used GM is the B&W TurnoverBall gooseneck hitch. Then you have a clean bed when hitch is removed. I would highly recommend the 20K companion for a rock solid hitch.
The 13 and newer RAM trucks have the pucks as a factory option or they can easily be added.