Where is the thermostat located on a gm 5.7 liter engine?

The 5.7L GM engine (like the Vortec 5700) doesn't have a thermostat in the traditional sense, like a separate housing with a replaceable thermostat cartridge. The thermostat is integrated into the engine's water pump. You won't find a separate thermostat housing to replace. If you need to replace the thermostat, you'll need to replace the entire water pump assembly.