Alfie, so was it necessary to rotate the drive gear on the 123 distributor? As you state, the rotor is tied to the drive gear and thus the rotor can only point in one of two directions (180 degrees from each other) if you orient the drive gear in the same direction as the 051 distributor that you pulled out. So if the rotor is pointing in the wrong direction when you drop it into place, I can only see adjusting it by rotating the drive gear on the 123 distributor. Does that make sense and is that what you did. Hopefully my explanation is clear as mud.
Thanks.