Yeah, that had me baffled.
Once I really thought about it I saw the differences, but what a mess.
It didn't help that I have a parts to everything all mixed up.

1969 Dodge Super Bee A12 (440 Six Pack, 4-speed, Dana 60 4.10)

1972 Plymouth Road Runner (400, 4-speed, 8.75" 3.23)

1974 Plymouth Duster 360 (360, 4-speed, 8.75" 3.23)