Eric,
The plot thickens. I looked online at a wiring diagram for a '51 CAR..no truck diagram was available (?). The schematic for the car showed a horn relay, so I would assume a truck would have one too.
The bottom line is that the horn circuit into the column/wheel area isn't made to pass the current required to sound the horn....only the power required to close a little horn relay.
Look at your service manual again. If it does show the relay, wire it accordingly.
It sounds like this might be the tip of the iceberg in the wiring department..a fire!
Stuart
