I just converted my 63 Dart to manual steering, I used a Borgsen 3/4 36 spline joint mated to a shortened B body inner column in my A body outer column.
We assume you are talking about the input shaft where the steering column bolts up. If the bottom "sector shaft", the diameter changed in 1973. Might help to relate what issue you are trying to solve.
Hi Bill, thanks for the information. I was looking for the number of splines that go on to the manual steering box and I finally got it counted and it is 36. Thanks for your help, Chuck