Jim - thanks for checking. Since that is a manual of unknown (to me) origin, I'll be a better referee than in the NFL and give the nod to Ford documents. I went back and checked seven single-year Ford car parts & accessories catalogs, as well as three different master parts & accessories catalogs, and updated the attached file.
The original design used part B8A-6026-A, per P&A catalogs through 1964.
In 1965 the part designated was C4TZ-6026-A.
In the 1975 dated MPCs, the 383024 number was used.
It dawned on me that the Obsolete, Supersede, Interchange catalog might help, and it sure did. The C4TZ-6026-A was replaced by (RB) 383024-S. There is no mention of B8A-6026-A.
Since all of these clearly state an "air bleed" function, these are not a simple plug. Confirmed by the one I carefully extracted a few days ago.