Paul;

Brake Lights and Horn are on the same (Fuse 2) circuit, so you should check fuse and its connections first....especially in Rhode Island where ocean air may have accelerated growth of oxidation and the resulting poor connections. Any functional tests on this circuit will need to be performed with IGN ON.

66 122 had a hydraulic Brakelight Switch with the well known and documented reliability issues (see: http://www.sw-em.com/safety_bulletin_4.htm )...after locating and repairing Brakelight issue, you may want to consider upgrading to the MUCH more reliable Pedal Position Sensing Switch...and apply ACZP to all electrical connections involved while you're at it.

The Horns themselves are also a weak area, because of how rarely the get used and their position in from of the radiator where they area optimally placed for corrosion attack...not to mention the weakness of the hornring switch and no relay...again, (only AFTER trouble is located and repaired) do I recommend considering an upgrade to add a relay...see: http://www.sw-em.com/122_horn_notes.htm

Cheers from Connecticut!