If I had a horn with two connectors the first thing I would check is if the connector going to the horn button is common to the horn frame. If yes, then you need electrical isolation of the horn body to body. The right size grommet and two washers would do it. If no, then no electrical insolation is need at the mount. I would not care for all that current at the wimpie horn button. Personally, I would wire in a relay where it can’t be seen. Do a little wiring change and no one could tell if it’s as original or not.

Six volt guy living in a twelve volt world