* 4.3L Vortec 4300 V6: A relatively small and fuel-efficient V6 engine.
* 4.8L Vortec 4800 V8: A common V8 offering a good balance of power and fuel economy.
* 5.3L Vortec 5300 V8: A more powerful V8, often found in higher trim levels.
* 6.0L Vortec 6000 V8: A large displacement V8 offering significant power, typically in heavier-duty models or those with towing packages.
To know the *specific* engine in a particular 2007 GMC Sierra, you'd need to check the vehicle's identification number (VIN) or the documentation that came with the truck.