The Camaro Nationals back in the late 1990's and early 2000 period, was run under the World Wide Camaro Club organization, which dissolved and got absorbed by Ecklers. The WWCC would hold national events at different locations each year. The events I attended were in Pigeon Forge, TN, Stone Mountain, GA, and Columbus, OH.
During that time, the WWCC had a 1000 point judge system and would award bronze, silver or gold award depending on points scored. If you received a gold award, you could then have your car judged for diamond class. There was a fee for diamond class judging, which took about four hours to complete. They used a very extensive check list, operating everything on your car, verified date codes, and evaluated the overall quality and accuracy of the restoration.
Many judges had extensive experience restoring Camaros, and some knew certain generation cars better than others. They had scrap books with year’s worth of facts and photo documentation from many cars, survivors, and clean original cars. The photo albums they had were as interesting to look at as the cars they were judging. When an item, hardware, etc. was in question, they would consult each other and compare notes and "photo facts" to make a decision on the item. This is how I learned that judges had to look thru their reference material for "common" used hardware, etc. during the time frame that car was built.
You very correct in that there was not a single "standard" for everything on our cars. The assembly manual was a standard work instruction and guide, but as we have seen, many variations are possible.
Over the years, I have met owners of very nice survivor Camaros that "get the itch" to restore their cars to look top notch like many we see at shows. I always praise the owner for what they have, and how rare a clean original Camaros are today, and encourage them to keep what they have as is. Our cars are only original once.
Good luck on your projects!