Will 2010 Silverado 2500 rear bumper fit on a 1500?

No, a 2010 Silverado 2500HD rear bumper will generally not fit a 2010 Silverado 1500. While they might look similar, the 2500HD is a heavier-duty truck with a different frame and body structure. The bumper mounting points, the bumper itself, and potentially even the receiver hitch will be different sizes and configurations. Trying to force it would likely result in damage.