Are all originals identical? I seriously doubt it. My chassis parts books (1928-37, 1939, green bible) show two covers ("long", "short") and matching bails and B- part numbers... with a third bail for 2 tooth sectors only (not indicating which cover to use, A- part number). The same base shows a B- part number 1928-37 and and 81A- for 1938-39. The big caution here is that sometimes Ford simply changed a A- to a B- in 1932, and sometimes had a different part which back interchanged (ie, 1932 works on 1931... 1931 does not work on 1932).
My experience suggests with a part with a 10-12 year run there may be different suppliers and running engineering changes which would not affect function but details would be different. So without exhaustive research to show what was actually installed original, or as a Ford supplied replacement with the same part number, the visual comparison is not valid to suggest what is "original".
The next issue the the competency of the reproduction. DOES IT FUNCTION? What is it a copy of? 1928?, 1934? 1937? Is it the "long" or "short" version. AND THE VENDORS SHOULD KNOW (And know to recommend the correct bail). And I am guilty of this... this is the first time I have researched this question. And yes, I hope to find a answer so I can serve customers better (as do many vendors).