I have a 2002 GMC k1500 Extended cab, 4WD. The owner's manual states it has a 7800# towing capacity, can I safely haul 8300#?

The answer to that has more questions like, what axle ratio, transmission and engine size. So with the largest size engine, unless Quadrasteer or HD 1500 is 5.3L, asume that and an auto tranny and 3.73 axle ratio. Now if you tow on level ground and haul dead weight not horses, it's possible with a brake control and good brakes on both trailer axles. But for insurance reasons and incase of an accident, you will have less liability problems if you stay within the truck manufactures limits which over rides the hitch manufacture rating if the reciever hitch is part of factory tow package.