Ok - took a look under my '39 Fordor Deluxe:
I've attached several pictures on what the connection on my car looks like. The spring is connected at the master cylinder end to a grooved boss on the clevis pin that goes through the master cylinder push rod. The other end attaches to the car by hooking through a hole in the crossmember forward of the master cylinder.
Pic 1 and 2 show the forward connection (one from inside the crossmember and one from the bottom).
Pic 3 shows the spring inside the crossmember (but doesn't show the ends well).
Pic 4 shows the spring connected to the clevis pin in the master cylinder push rod. Unfortunately, as you can see, my brakes have not been touched in a very long time (I won't say original but there's got to be 40+ years of grease buildup on the brake/clutch shaft housing that makes it hard to see the spring connection.
To give you a better idea of how the spring connects to the clevis pin, I've attached a picture of my '47 COE master cylinder and the brake spring (Pic 5). The connection method is identical and this picture doesn't have the grime my '39 does.
Hope this helps.
Dan