The 51's used two different horn ring springs. A heavy version and a light version. Could be your heavy version spring is bottoming out before making contact.
Going by the parts manual, original Ford 49-51 used the same mounting bracket for all but the Station Wagon. If mounting Unity spotlights Convertibles and Victories used specific brackets.
The two long brackets are part # BA-16898-A
Brace (Hood Lock Support to Radiator Support)
I'm thinking Bracket (Transmission Overdrive Manual Control Handle & Cable)- on Instrument Panel Part #AB-77250-AP....but not sure.
Never tried it myself but it might be worth considering....
Use a two pin security screw driver for use with two drilled holes in a screw head.
Check them out on McMaster.
Try here for wiring products...
https://brillman.com/?gclid=CjwKCAiAhKycBhAQEiwAgf19ehr6ty7N4loHdV4FgPG0I-Z9R9IGdUqNkm1oMVaArdsHY3VvvSAZiRoCirAQAvD_BwE