Then add a double rocker switch so you can flip between then OEM horn and air horn.

 

I run mine with a foot switch from a RV toilet, mounted to the left of the brake pedal. I had it tapped in to the regular horn, but found out right away folks didnt appreciate the "toot" when I set the alarm.

I find it works great, and after I got used to it, I can do a panic "honk" just as fast as the steering wheel button.

 

I got a momentary switch from Radio Shack and fabed a bracket out of sheet metal and mounted it on the floor under the E brake . Can't see it unless you bend down to look under the dash .