Unable to cross reference the following rocker arm numbers in my parts books #838254 #838255.

Could someone please help?

dandyd

Note that the rocker arm stands for 1937 and up use casting #838246.Could the rocker arms be from 1937 and the number was changed in 1938?-that would be casting #838997 and 998 in the book-part #838993-994--There is no history of the 838254-55 in my 1939 parts book..or the 1940,41.44,47 or 48 books.