Ty,
Are you referring to the very smallest spring in the picture? I believe that is the one that hooks onto the center or middle of the secondary shoe and then connects to the stamped sheet metal post located at 3 oclock on the backing plate. If so, let me know if that is the one you need and I'll check my brake parts inventory. According to my master parts book, if that is the spring, it is the same for your '37 as it is for my '40. Let me know and I'll check for you.
Whit