2004 Chevy Silverado Upgrading Suspension

Towing capacity is determined by the amount of torque produced. It's the ability of the vehicle to get the horsepower to the road. There is not much you can do to increase the tow capacity of a 1/2 ton.

Have you an idea of how much weight your wanting to drag?

10 is way too much for that payload. I wouldn't pull more than 5K. If it sags too low with a 5K load, overload springs would be good in that instance.