Have you stripped a hole in the rear deck lid where the hinge bolts to the deck lid? Not to worry. It is easy to repair:
The bolt on the left is a normal 8 mm. The right side has been drilled and tapped to 3/8 x 16. This is the plate that is inside the rear deck lid. I cut up a rear deck lid and took one out to show how it is done.
Drilling and tapping it to 3/8"-16 American is no problem. You should be able to do this with the deck lid on the car. The OEM GM bolt is 8 mm. Once stripped out it leaves about a .300" hole. The slot in the hinge is plenty large to accept a 3/8" bolt. There is plenty of steel to tap. It is 2 layers. One thin angle piece and a heavy flat piece of stamped steel and they are welded together. You have to drill the stripped hole to .312" first or you will probably tend to break a tap. Then use a 3/8 x 16 plug tap. It seems to be a somewhat hard steel and kinda hard to tap. So use a new or newish plug tap and cutting oil and be slow and careful. Once tapped to 3/8 x 16 it appears it is as strong or stronger than original.
If you have one of my rear deck lid strut kits or want to add one of my rear deck lid strut kits I can make you up a strut with a 3/8" bolt instead of the OEM 8 mm bolt.