I don't think on these old bikes there is a definitive ANYTHING, or this forum probably wouldn't exist. If you have an unmolested, original bike with no miles, that would be somewhat "definitive". I wasn't alive or mostly a toddler when most of this stuff was built based on production, sales, and profit push. That said, this is a book depicting the restoration of a 63 & 69 unit construction by some knowledgeable people.
I was "schooled" by a fine gentleman on this forum to not believe it because it's on the internet or someone tells you so, believe it when you see it on an original bike.
Have fun restoring your bike. That is the most important of all.