To find the exact towing capacity for *your* specific 2003 GMC Sierra 1500, you should:
* Check the sticker: Look for the sticker on the driver's side doorjamb or inside the glove compartment. This sticker lists the vehicle's specifications, including towing capacity.
* Consult the owner's manual: Your owner's manual will have a section detailing the towing capacity based on different configurations.
* Use the GMC website's build-and-price tool (if available): While you can't build a 2003 truck, older brochures or archived information on the GMC website *might* offer some guidance, although it might be difficult to find.
Without knowing the precise configuration of your truck, I cannot provide a definitive towing capacity. Expect the range to be somewhere between 6,000 and 9,000 lbs, but this is just an estimate. Always rely on the information found on your vehicle's sticker and owner's manual for the most accurate data.