The Most Devastating Engineering Miscue Found in Early A-Bodies

my68barracuda said
Not exactly only an A body issue. Does anyone have information on why Chrysler did three different versions of the 8.75 center section, 741, 742, 489?
There is just enough difference between the three to make the gear sets non interchangeable, but not enough of a difference to make one truly superior.

There were actually at least 5 versions. They started in '57 with the 985 case. There was also that goofy one they used in some of the mid 60's slant 6 B-bodies where some of the internals didn't fit any of the other 8 3/4's. It looks just like an 8 3/4, but, the ring and pinion is actually an 8 1/4.