The harness comes with the taillight. The numbers for the taillights on that page are wrong, and I have yet to confirm the harness p/n. Get a VIN off an 03 Silverado and call up your local Chevy dealership and ask them to look up a part. I know my local dealerships have been real helpful in finding the right p/n.TheLlama said:slow down JJ! here man, this sould have what u need + MORE!