The original Chrysler part number for the HP dual point distributor vacuum advance was 1843034 then superseded by part number 1881757. Both numbers are hard to find and usually near $100 when found.
FYI....the 2 bbl advance will mount on the distributor, but the arm will not connect to the plate. Usually the aftermarket models do not fit as I discovered on my 65 FS with PO repairs.
The 1843034 advance has a fairly narrow application range: 1965-67 273 HP and 1957 Plymouth Fury and DeSoto Adventurer cars. No wonder they are hard to find.
Good luck on your search