Enduro rules genesis:
The Nelson Ledges Longest Day 24 hour rules were refined over 17 iterations.
The DC Region used these as the basis for their 1.5 then 4, 6 and 12 hour rules starting in 1993.
These DC rules were shared with New England Region as the basis for the NEDiv short enduros around 1998. These rules were also shared with Central Florida Region as the basis for their Longest Night 24 hour races at Moroso circa 1997 and with North Carolina Region as the basis for their 13 hour race a bit later. I am unsure how the west coast NASA 25 hour race rules evolved.
Each of these east coast Regions made some changes to the original rules set based on local conditions and sometimes personal preferences.
Ultimately, today an east coast team must have different execution strategies based on which race is entered under the differing rules sets. It's time to standardize the safety related rules and get them in the GCR (e.g. fire bottle pin in or pin out, grounding, clothing, fueling, etc.). These are the things that should be in the GCR. When and how to work on cars, how to time pit stops, how to equip cars, etc. should be left to the supps. They, for the most part, are already addressed by the individual series rules but there are some differences that should be standardized.
Regards,
Chuck