And to add to my confusion.
For the 1968 parts book, the distributor should be 2875358, which I believe is a single point Chrysler unit (not Prestolite).
For 2875358, the correct vacuum control should be 2875096.
Attached is a FSM photo of Chrysler and Presolite parts breakout. My 2875358 looks like the one on the left (Chrysler) but 2875096 vacuum control looks like the one on the right (Prestolite).

So is the FSM wrong or parts book wrong?

This annoyance doesnt stop. So I was able to find an NOS shaft about as close as possible to mine. This is for the 383 manual trans A-body distributor versus my auto. Short of an exact match, probably as good as it gets. I am smiling.
I get the box today and open it up, NOS box, sealed tight with original staples, never opened, wrapped in wax paper, feeling good. Size up the shaft and it is perfect length. Then I look and dont see the hole for the roll pin. NOS shafts dont come with this hole??
Yes, I can drill it, but man, this is not getting any easier. Drilling on a round hardened shaft is gonna be tough. I have a drill press, but need to come up with a way to ensure this thing does not move. I guess clamping it on some wood could work.

Interesting note. The 383 shaft has a different arrangement of the advance weight holes then I recall seeing. They are on an angle, unlike the 440 shaft I have and other distributors have. Weights also dont throw out as much before the springs kick in.

Good luck with that , 383 manual trans A body used a PRESTOLITE distributor, that is why you see a difference. Also not the numbers , the one on the left has 24 degrees mechanical advance , the right has 31 ... multiply the stamped number by 2.

I have a bunch distrbutor parts, I might have that shaft NOS ???

6PakBee- The problem is that the shaft in the one he has is too long. So he's trying to find the correct shaft or a correct example to compare with.

NJmopar - Did you notice the FSM part number and the Parts Book stamped numbers don't match?
2875xxx vs.
2857xxx
Since all the part book numbers indicated distributors are stamped 2875 xxx, I would guess that is correct. Yes - I checked '69 Dodge FSM and its 2875. I'm going to guess the vac advance you have is correct if it fits even though it is the design shown with the prestolite.

The weights are the same, p/n 1881 955
I think the only difference between auto and manual versions will be the governers (cam & stop plate in parts diagram) in the package with the shaft assy.
Cam and stop plate: auto 2642 848, manual 2875 380.
the springs package: auto gets 3004 169, manual 2932 707.

If you can find a NOS shaft 2875 175 in your stash, this may help me understand what is going on and keep my mental state solid.

The 68 FSM (attached) says both the manual and auto are Chrysler built. Also, take a look at the advance spec stated for at the distributor (which would be the number on the shaft?), the 15.5 for mine would be below the upper spec for 2500 RPM.
The 68 parts book show the same part numbers for both manual and auto distributors for the cap, rotor, points. Just the shaft and weight sets are different. Prestolite would be a dual point and different internals, I would think.
Are the FSM and Parts book wrong?

6PakBee- The problem is that the shaft in the one he has is too long. So he's trying to find the correct shaft or a correct example to compare with......

I am working on 68 383 GTS convertible. Trying to get as close to original as possible, within reason. For example the dist I have is correct part number on housing but dated 69. I can live with that.......