It would make little sense for someone to remove the horn relay to the extent that you couldn't see where it was located. If the horn didn't work, most people would either ignore it or fix it. My '67 has that relay under the dash, on the inside of the firewall. A '65 wiring diagram that I looked at, shows it under the hood, but anything is possible. You had the wheel off. follow the horn wire through the column plug and see where it goes.
[img]
http://www.rowand.net/Shop/Tech/images/GmAlternatorIdentification.jpg[/img]
The two wire plug on the SI internal regulated alternator, plugs into the top or side depending on orientation. The DN alt. with external regulated has a two wire plug, that plugs in from the rear. The reg, if it has one, might be on the radiator support, drivers side.
Three speed column shifts have the back-up light switch on the top of the column, under the dash, at the firewall. Automatics have that switch and neutral/park safety lock-out switch in the same location.
P.S. Ignore the wiring on the DN and the SI. Contrary to popular belief, it's wrong. The single wire on the CS is the "L" wire and goes to a resistor and/or idiot lamp and then to the ign. switch. The CS-130D must have the "L" and the "I", both connected, but through a lamp and a resistor, respectively.
