I Am not nearly as smart as you with the numbers . I can only confirm what I have seen with my own eyes. I had many 69's and I have seen the bell style on some of those cars. This blue 69 I know had them for sure. The complete rear is still here. None of the 68's I had ever had them. Usually if the axles had balance holes they had the bell style drums. If they only had the flange nut access holes they were standard drums.
Yes the axles were also different in the early 8 3/4 rears.
I have both styles if you would like some pics. The axle flanges are different