1. Chevrolet C/K 1500: The regular cab, short-bed model with the 5.7L engine has a towing capacity of 7,100 pounds.
2. Chevrolet C/K 2500: The regular cab, short-bed model with the 5.7L engine has a towing capacity of 9,500 pounds.
3. Chevrolet C/K 3500: The regular cab, short-bed model with the 5.7L engine has a towing capacity of 10,000 pounds.
These figures are based on properly equipped vehicles with the appropriate trailer hitch and cooling systems. It's important to consult the owner's manual or specific model specifications to confirm the exact towing capacity for your 1999 Chevrolet pickup with a 5.7L engine.