John, your bell housing is a bit different than the AD ones, with those two "windows" near the top where it bolts to the block where the AD housing I have is solid.I see now that my assumption that the hole in question being lined up with the clutch arm ball (I was remembering it as a socket, but that's on the arm itself) is incorrect.
So the mysterious hole is still mysterious. Nothing there to adjust, but maybe a spot for engaging the flywheel teeth to bar the engine over?
