Duster bell housing

1972 Twister /6, thanks
Okay, slant 6 may be different, I'm not as familiar with those.
From slantsix.org:
4 Speed Transmissions transmission (slantsix.org)
Bell housings

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Slant Six owners have two bell housing options to mate G/RG blocks to 833s. The original 1964-66 Slant Six four speed bell housing is a great candidate and accepts any A-833 with a 4.35" IBR profile. These units were all cast iron. While these bell housings are becoming increasingly hard to come by, the inspection plate, dust shield, clutch fork, and fork boot can all be swapped-over from a Sixties G/RG with an A-903 three speed. The casting numbers for the early cast iron bell housings are 2463025, 2463027, and 2468431.
Mopar 3-speed Info. (Click Here)

A much cheaper and plentiful bell housing to use is the 1975-81 A-833 Overdrive Slant Six bell housing. The upshot of this bell housing is that it is cast aluminum, the downside is that it only accepts A-833s with 5.125" IBR profiles. When looking for donor vehicles in salvage yards, don't' walk past late seventies slant six three speed cars. Chrysler used the same bell housing for both A-833 Overdrives and three speeds by placing both bolt patterns on the same bell housing. A casting number for this bell housing is 3743645. (This is a 1975 number, no doubt later bell housings used other numbers.) The Overdrive bell housings use a unique clutch fork mount that you will not find on regular three speed or four speed bell housings. Make sure you keep track of the correct fork and its mounting stand that bolts inside of the bell housing!

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The Overdrive bell housings can be modified to accept either the 4.80" or the 4.35" IBR. A ring must be fitted to the bell housing to reduce its IBR hole from 5.125" to 4.35" or 4.80". This ring must maintain the hole's exact center! A skilled and caring machinist should be able to accomplish this without issue. Good planning would provide the machinist with the bell housing and IBR you plan to use so a perfect fit can be achieved.

Once upon a time Chrysler made IBRs that fit the standard 23-spline case and mated to the 4.80" and 5.125" bell housings, however these appear to have been discontinued and snatched up a while ago. An additional option for someone trying to put a close ratio 4.35" IBR A-833 behind an Overdrive bell housing is to use an Overdrive front case and IBR and replace all the internal parts with those from a closer ratio four speed. This swap requires changing all gear sets, shafts and the countershaft.