you need these. http://www.amazon.com/HELLA-760688000000-003399801-Supertone-Bracket/dp/B000CRZXPI

they work exceptionally well at tell someone to get the fuck out of the way.

I once watched a serious case of road rage happen in front of me on 85S. One guy kept swerving into the lane of the other guy, nearly hitting him multiple times. I got up as close as I was comfortable doing (my car had excellent brakes just in case) and just laid on the horn with the hellas. They got the hint and both chilled out and went about their business.

Wouldn't you know, I'm about to wire some horns into my brothers 78CB750! But Yeah I have two hella super tones http://www.amazon.com/HELLA-003399801-Supertone-High-Bracket/dp/B000CRZXPI and wired a relay. Your original wiring probably can't supply enough current for the aftermarket horn. If it hasn't failed it probably will soon fail if you're trying to push current like that through a factory wiring harness. Look up how to wire a relay it's really simple,

+12v into relay from battery (terminal 87),

+12v into relay remote/trigger basically the positive lead that attaches to your factory horn now goes to terminal 86

Ground terminal 85

And finally +12v out from relay that goes to your aftermarket horn Terminal 30

Then you ground the horn wherever you want.