The basic Chrysler A-833 transmission was introduced in 1964. Since then there have been many differnet versions, updates and modifications. There are two different lengths: A/F-Body (short) and B/E-Body (long); there are coarse and fine-pitch gears; Four different production ratios; and half -a-dozen specialty ratios like the race "red stripe". From an interchangeability standpoint there are basically three versions: A small spline: A large spline and the Overdrive.
There are also three drive pinion bearing retainer pilot sizes (that is the part of the transmission that pilots into the the bellhousing) that serve as the basis for separating these three transmissions. This is important when buying transmissions and belhousing seperately. (As I did when I bought a aluminum belhousing with a 4.354" pilot opening and a trans with a 4.807" pilot O.D. - which did not fit. -- A little machining of the bearing retainer down to match the 4.354 on the bellhousing should fix this.) Also, if you have a trans with the large 5.1, Chrysler makes retainer to replace it to fit 4.8 (Part No. P4529696) or fit the 4.3 (Part No. P4529659).
In 1970-1971, the 340 had a small spline and the small trans-to-bellhousing pilot O.D. (4.354"). The 440 and 426 Hemi, '70-'71 had the large pilot (4.807") and large spline. The '70-'71 383 had the small spline and large pilot. The large pilot bearing was introduced in 1968. The early trans (64-67) were all small pilot models. The 4-Speed overdrive transmission intoduced in 1975 is a small spline unit but has an extra-large pilot rtainer O.D. of 5.125"
The drive pinion retainer pilot O.D. changes are caused partially by a change in the drive pinion itself. The small drive pinion (#307) is used with the small pilot O.D. The large drive pinion bearing (#308) is used with the large pilot O.D. The 1968-1969 383 used the #307 bearing with a special large pilot retainer (PN 2892256). From 1975-1980 the A-833 has used an extra large pilot (5.125") usually with the 308 bearing, but some of the 1975 models came with the #307. See chart below for drive pinion bearing retainer usage (1970-1980)