* 4.3L V6: This engine had 12 valves.
* 4.8L V8: This engine had 16 valves.
* 5.3L V8: This engine had 16 valves.
* 6.0L V8: This engine had 16 valves (in the 2002 model year).
Therefore, there's no single answer. It depends on which engine was in the particular truck.