A833 real seal and reverse indicator switch

Not counting the '64/'65 ball and trunnion units which don't apply here, all long tail (B, C, E, some trucks) 833s from '66 onward had 30 spline output shafts, same as a 727.
A (and later, F body) short tail 833s had a smaller diameter 26 spline output (same as a 904) in '66/'67, except for the mid-year '67 383 GTS and Formula S cars, which got the first of the short tail 30 spline output shafts. In '68 and later years they went to 30 spline across the board.
The reverse sender uses what amounts to a crush sleeve to seal it.