1975 duster

About 1/2 way down there is a drawing of an A-833 and notes indicating it got an O.D. 4th gear in mid-1975 for 318s and/6 which would make it likely available for the 1976 model year

.Chrysler A-833 four-speed manual transmissions —...

Wikipedia also shows the A-833 OD version being used from 1976 through 1980.

List of Chrysler transmissions - Wikipedia