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.