Geo Hahn
Yoda

Offline
It's not so much that the "change point is a bit vague"; rather, it's a matter of North American market cars v. those built for other markets.
In the case of my car at least it does seem to be vague. Based on the chassis number (29272CT) the body was built in February 1964 and thus would have the small lights. based on the Commission number (CT36536L) the build was completed in September of 1964 and would have the large lights. These are also the BMIHT numbers.
Not sure what happened on that 7 month production line (the engine is also from February) but I figure I have some flexibility as a result.