The same thing is true with the emblems. I laid out the holes on crosshatch paper from the assembly manual. Believe it or not, the left side and right side were not identical. I forget which is shich, but one leaned down, from left to right, and the other leaned up from left to right.
I made a template from a cereal box, and outlined the "Camaro" Then I taped it on the car, and stood back. Adjusted until I felt it was perfectly level, and drilled.
Basically did the same thing for the rear spoiler. Aligned the spoiler without the studs,and marked the position on the deck lid. Then marked the stud holes on the template, and drilled.
You see a lot of spoilers with the stud bosses hogged out. I think that's because when you tighten down on the nuts, you put alot of strain on the spoiler. Then when you slam the deck lid, you put even more on it. If you have a 35 year old spoiler, it's probably a little on the brittle.
What I did was slide a speed clip over the stud, and then install the stud in the spoiler. I epoxied around the speed clip to hold it in position. Then I used a small rubber washer over the stud to space the spoiler just off the deck lid. Now when I tighten the nut onto the stud, the strain will be between the speed clip and the nut, rather than between the spoiler and the nut.