Where is the thermostat located on a 2000 GMC sierra 6 o liter 2500?

On a 2000 GMC Sierra 2500 with a 6.0-liter engine, the thermostat is located on the engine block, specifically at the engine's front near the water pump. You'll find it underneath the thermostat housing, which is connected to the upper radiator hose. To access it, you may need to remove the housing and the hose to replace the thermostat.