BUTT CHANGE : Sometimes we cant find a distributor for a specific project. That may require a butt change.
The top of the donor unit ( that has the features we wish) is cut off and mated to the lower end of the distributor that fits the engine we wish. In this case we used a Mallory flatcap Marine unit with mechanical advance and mated it to a 1952 337 CI Flathead with no mechanical advance . Perfect in all worlds. The 337 lower end is mated to the top half of the mallory, shaft is spliced to the Mallory and its done.
New unit mounts exactly like the 337 should and offers the engine full mechanical advance ( adjusted to 337 specs) , the use of the red Mallory distributor cap further enhances the project!!!! .