The production year for any model year begins with the fiscal year, which begins July 4 of any model year. Introductory show units have a build date on the door tag - a "scheduled" build date - of July 4, or 04G on the tag. None are actually built on that date, but it is the earliest scheduled build date that you can have on any model year Ford product.
The end of any model year is going to be July of the following year, when final assembly of any model year's Ford products happens. Such cars have a scheduled build date as late as July 31 of the second year, or 31U on the door tag. It might happen that a car could have been scheduled for the second August, which would have a V for the month, but I have never seen or heard of such a case.
So there you have it - the earliest and the latest. If you own a factory shop manual it explains this in great detail in the introduction.