Slip Yoke ? for 1966 Barracuda F/S - 833 trans

The 66 and 67 A body 273 4 speed uses the small 904 slip yoke. I have had both 66 and 67 original 4 speed Formula S Barracudas. The 67 A body 383 used the large slip yoke. 68 and up A body use the large, 30 spline slip yoke, same as the 727. 1.675 is the large, 30 spline slip yoke, who can say when the change over occurred?