Clean your glasses Cap'n (it is a long read), and have a gander at this thread:
Final tread on transition from 65-66 model yr!!
You are not the only one that has been misled by the factory literature; they did their best to obscure the 65/66 transition. Further, the Kardex dates that we have the easiest access to for dating the cars is actually the Invoice date. Comparing this date to the dates in the factory production book shows that the Invoice date can be up to a month later than the production line completion date. So while the Kardex points to a significant change (paint codes & dash kneepad, etc that appears to be the physical change in the model year) about the end of July, we can infer a change on the production line near the beginning of July.
One of the tricks in the literature is that the factory does list VIN's at the end of the Calendar year but not for the Model year in the 1964, 1965, 1966 period.