Slant 6 with 4 speed

They stopped putting the 4 speeds in the 6 cylinder A's in 1966 when they went to the 2.66 ratio 1st gear and didn't use them again until they came out with the 4speed OD trans that uses the 3.09 ratio 1st gear like the 65 and down 4 speed used in the A body. Not certain what year the OD 4 speed was introduced but it was after your time frame.