REAR BRAKE DRUM differences 1939 and 1940? part nr. 75035 (1939) and 75542 (1940)

[gsottl]

Hi AMCA members!

Can anybody tell me the difference between 1939 and 1940 Chief/Four rear brake drums?

I found out they have a different part number (75035 for 1939 and 75542 for 1940) but have no idea what the difference is. I know of course that the ancore plate is diffent, but what is the change in the drum?

Can I use a 1940 drum on a 1939?

Thank you for your input and ideas!

Cheers,
gsottl