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 WarningCylinder Head Removal - Left Side Engine Block Cylinder Head
Remove the two-front M8 left cylinder head bolts-(1) and discard.Remove the left cylinder head bolts-(2) and discard.Remove the left cylinder head-(3).Remove and discard the left cylinder head gasket-(1). ...