Repair manuals (like a Haynes or Chilton manual, or a factory service manual) will provide the exact torque specification for your particular truck's engine. Trying to find the information online without knowing the precise engine (e.g., 4.3L V6, 4.8L V8, 5.7L V8, etc.) is unreliable and could lead to damage.
Over-tightening a knock sensor can easily strip the threads or damage the sensor itself. Always use a torque wrench to ensure proper tightening.