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?

IMG_0418.JPG
FSM page

IMG_0419.JPG
2875096