Something that hasn't been mentioned yet. In 73 the B bodies went to the rubber isolated K frame as well as the isolated perches on the diff. And all the springs had large front bushings to increase the smooth ride too.
Chrysler was smart enough to equip the 440 4 speeds with a Dana 60 from 67-72 so they wouldn't have warranty claims from guys dumping the clutch. And they had smaller front spring bushings to lessen the isolation.
No Dana's after 72 therefore no 440 4 speeds.
And even if they had offered a 4 speed, would they have done the whole rubber isolated deal on a Dana? Nope
