Go to a generic auto site. 421 is A Body and 422 is B Body.
In that case; I'll tell you what I have found;
The A-body short tail overdrives come in two flavors, one with the big mainshaft for V8s that takes a 727 yoke
and the smaller one that takes the 904 yoke.
Each of these uses it's own rear bearing and the tail is finished out for each matching bearing.
There are also two non-interchangeable gearsets
The V8 has a 21tooth overdrive gear, and
small mainshaft has an 18tooth overdrive gear.
Between these gearsets no parts are interchangeable save for the MS low.
The synchronizers are different front to rear but otherwise swap between the V8 and the /6.
All front bearings are the same AFAIK.
The rear bushings and seals are also different, for the matching yokes.
The mainbox,retainers,sidecovers, and forks can all be swapped around.
You can make a longtail by robbing a chevy MS and tail off an 80s pick-up truck, with an A833 in it. You can rob the whole trans but the Input is distinctly Chevy, and from what I remember, the gears were either different from the Mopar. or they were /6 stuff with the weaker 18t od gear.
