During that period of time (1968-69-70) current model year production, new orders were terminated on/around 30 June of each year. Which would generally mean that the last cars produced for that year's models would come off the assembly line within a couple of days afterwards. At that point each plant would begin transition for production of the following year's models. That time frame might change a little depending upon the significance of the changes in the car and production processes for a specific model.