Jeff, I know I'm late to the party here, but I have your answer, if you still want know. The bracket was just a simple piece of strap that was bent at a 90 degree angle. It bolted to the side of your frame and to the end of the rusty bracket in your picture.
The data plate on a 1937 truck did not tell anything about the truck, itself, but the series. All 1937 1/2 tons were series GC. The tag would look the same if the truck was a Pickup, Panel, Canopy, Suburban, or Chassis-Cab.
Other info on the tag is place of manufacture, month of manufacture and sequential number of manufacture. I hope this helps. Sorry to be so late.
Mike
