john,
I mounted a set of air horns on the 2003 Yellowstone we used to have in the front right below the "toy" horn location.
Made a bracket and bolted it to the frame and the air horns mounted on it. I used the wiring for the present horn, just tapped into it for the valve coil and just used one of the ports on the air distribution block for an air supply to it. Kept the original functional just in case there was ever a problem with the air horns.
I bought the air horns on eBay really reasonable.
Our present coach came with air horns mounted on the roof, wish it didn't because now I have to climb on the roof to clean and polish them.
Ron