I know there are a lot of keep it original owners here but looking for a Dual master cylinder
that does not need any or minimal alteration for a 46 -54 plymouth.
Not much response yet. . .
You might try the same question over on the forum at https://p15-d24.com/forum/4-p15-d24-forum/ as their focus is on cars of this era and a fair number of members who are interested in various brake system upgrades.