Are All B Series Starters the Same?

Registered. From what I know all b-series trans cases are the same bolt pattern and all the starters are the same.

Are all B Series transmissions the same?

From what I have read and seen, all B-series transmissions are pretty much built the same except for minute differences. The one outstanding point are the synchros that may differ in each transmission. For example, a B16 tranny is an ITR tranny minus both the LSD and the superious synchros that are used.

Are D Series and B Series starters the same?

yes same number of teeth and the "kick" length is the same. I have found the "gearbox/reduction" part is identical in both D and B series starters. I could swap them. Bearings are also the same that fit into the housing.