Apparently, CASCO, a major supplier of parts for Babybirds, does not have it correct then. Their ad shows it is a 7lb cap..
Perhaps...............but it may depend on their reference source.
page 23 of the Compilation of Product Service Letters dated 12/29/1954 states the cap is to be of the 12 - 15 lb variety instead of the 7 lb rating used for 1954 products. Also is a footnote to revise the 55 Ford car Shop Manual (page 338 secton 8) to read "Cooling system is pressurized to 12-15 pounds on all cars and Thunderbirds." The 55 Shop Manual (which I don't have) should state 7 lb cap originally - so that may be the source of confusion.