I remember you posed this question a while back but rec'd no responses. Please post a photo of what you are dealing with, if possible. Do you have a part number? When I replaced the springs on a 1940 Ford door lock, I had to bend the hold down tabs after heating them. If the break, you can braze them back on - which is what I did. Use a very small welding tip.
Also is it the right or left hand door latch. Try a Google search.
https://www.bing.com/search?q=1939+m...ANAB01&PC=HCTS