For service and parts needs, visit your dealer. You will receive genuine GM parts and GM-trained and supported service people.
Genuine GM parts have one of these marks:

Vehicle Care
California Proposition 65 WarningInstallation Procedure
Drill 8 mm (5/16 in) for plug welding along the edges of the tail lamp
pocket as noted from the original panel.
Note:
Clean and prepare the attaching surfaces for welding.
Position the tail lamp pocket on the vehicle.
Verify the fit of the tail lamp pocket.
Clamp ...
Vehicle Positioning
At times, the position of the vehicle on the map could be inaccurate due to one
or more of the following reasons:
• The road system has changed.
• The vehicle is driving on slippery road surfaces such as sand, gravel, or snow.
• The vehicle is traveling on winding roads or long straight roads.
...
Vehicle Load Limits
It is very important to know how much weight the vehicle can carry. This weight
is called the vehicle capacity weight and includes the weight of all occupants,
cargo, and all nonfactory-installed options.
Two labels on the vehicle show how much weight it may properly carry: the Tire
and Loadi ...