The 742 was available as early as the 67 model year, and was phased out in 69 when the 489 was implemented. Although it’s funny, the “657” cases of 1964 were the same size as the 741, and they came in all Max Wedge and Hemi cars, and although the 741 gets a bad name for being the “small” rearend, somehow they managed to survive 100’s of neutral drops.