Some updated information. In a previous post I see a picture with part number C7ZB-17664-B, so I took at look at a few MPCs, picture attached. Also I checked the one from my car, and it is a -B as well.
In the January 1967 version, there is a note that says C7ZB-17664-A is what C7ZZ-17664-A is marked as. This same note continues in the August 67 version and is carried on to 1975 as well. There is no -B reference. The MPC is simply a reference point, not gospel. The first picture shows all three MPC versions.
Since we were on the discussion on wiring changes - from individualized color coded plugs to a single connector assembly, I did some digging there. The connection to the W/S washer pump is on harness 14401. In looking at the shop manual, figure 34 shows the later single connector style, which makes sense. Refer to attached picture 4. The MPC lists four different applications - with and without the GT equipment group option (fog lamp), and with and without tach. The 67 MPC lists four part numbers. The 68 MPC takes the four part numbers through two changes, dated 1/3/67 and 4/15/67, resulting in 12 different part numbers. Refer to pictures 2 and 3. Picture 3 is a table I created which is intended to make it easier to follow the changes.
Based on this alone, my guess is that the 1/3/67 change instituted the single connector replacing the individualized plugs. That is based solely on the information described above, and is a starting point for discussion. As always original unrestored cars are needed to validate or correct these assumptions, but it is an area difficult to get a camera on.
Richard's car, built before mine, has the single connector. Mine has individual plug in connectors. Both are SJ cars.
Also on the topic of 14401, my GTA has a single gray wire in parallel with the wrapped harness, but not part of it. I don't see why, then, the MPC would list a different 14401 between non-GT and GT, at least for before 1/3/67.
The answer perhaps is that there was a whole lot of change going on, and it was not worth chasing every last change with MPC revisions. Mechanics can adapt at the point of installation.