Dodge has been using 17" wheels standard since 2002 in the 1500 and 2003 in the 2500/3500 series. They probably went to 17s to fit the massive brakes inside the wheels, the Front Rotors on the 2500/3500s are about 13" in dia. I don't think a 16" wheel will fit that size rotor inside
actually they are 13.94 or something, and no nothing smaller than a 17" wheel will fit. The factory dodge wheels fit and so do the factory H2 hummer wheels. I've heard stories of certain 17's not fitting but have never seen it with my own eyes.