No, they are all 1966. Correct me if I'm wrong, but the CRG info clearly shows how to decode casting dates. All three components, case, side cover and tail housing were cast in Dec. of 1966.
That's L 19 6 and L 14 6 and L 21 6 All December of 66. And then the whole saginaw transmission was assembled on the 27th day of December 1966 for a 1967 model year car.
That is how the CRG website describes how to interpret theese numbers. Is the website wrong?