That Small pin with the ball bearing in it (#39??) Is a sticky wicket. In all the ones I have seen, that ball is seated in there either by a pinched tube, circlip or something??? But have never seen one with that ball removed.
That Pin seems to be one of the most elusive BSA parts and MOST BSA Projects I have or have worked on 99% of the time that pin is missing. I could use about 12-14 more of them as I have a number of A65 projects in very extreme basket case form and I have only 1 of those pins.
I cant say for ALL unit BSAs, but its quite common to segment the pushrod shaft and add a small ball bearing between 2 sections of the shafts and some shops recommend it. I believe Dyno Dave Comeau talks about it as well as how to stop gear oil migration onto the clutches, but I have also seen it mentioned in MAP cycle install instructions for their belt drives and pressure plates