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 WarningRear Suspension
Specifications
Rear Suspension Components
Rear Shock Absorber Upper Mount
Rear Shock Absorber Upper Mount
Rear Shock Absorber Upper Mount
Rear Shock Absorber Upper Mount
Shock Absorber Assembly
Upper Dumping Ring
Rear Spring
Lower Dumping Ring
Rear Axle Bushing
Rear Ax ...
Reporting Safety Defects to the United States Government
If you believe that your vehicle has a defect which could cause a crash or could
cause injury or death, you should immediately inform the National Highway Traffic
Safety Administration (NHTSA) in addition to notifying General Motors.
If NHTSA receives similar complaints, it may open an investig ...
Installation Procedure
Clean and prepare the attaching surfaces for welding.
Position the roof rear header panel (1) on the vehicle.
Verify the fit of the panel.
Clamp the roof rear header panel into position.
Spot weld accordingly as noted from the original panel.
Apply the sealer ...