I got a vac-adv for my '54 from one of the truck supply places. It had a sort-of "key shaped" post to engage the link on the distributor. That was not correct for my unit.
I went to a different supplier and got one with the correct link for my distributor. It used a screw with shoulder to engage the link on the distributor.
I don't know which years use these two different kinds of linkage.
