It depends on how involved you want to get, and how hidden you want the horn.
I decided to fit the Stebel Nautilus (also branded as a Wolo Big Boy) air horn under the tank.
Here's the horn with attached compressor. I used the steel cutoff wheel on the dremel to cut off the plastic 'ears' that hold the horn(s) to the compressor.
Then I painted the compressor black and mounted it to the bottom of the ARK. Yellow arrow points to the bolt.
Blue dashes are the air line. You can see the relay riveted to the ARK, near the rear brake reservoir - it has a yellow wire and a clear wire visible. The yellow wire is one of the leads from the 15A inline blade fuse.
I mated two lines together to make the air line, end "A" stick is stuffed into the horn inlet. This is an example, the line I used ended up way longer.
End "B" fits over the cast outlet of the compressor. Both ends were sealed/secured with RTV, also the junction is sealed and clamped. I used a clamp at the compressor end too.
The horns were tucked and zip-tied up under the tank, within the frame, wiggled in from the left side. It was a very tight squeeze, you really have to trim off all the unnecessary plastic from the horns, and rotate them as you get them in. I had to remove the tank and also temporarily removed the (?) ignitors that hang from the frame. You'd think that the plastic horns would melt in that location, but no part of the horns touch engine or oil cooler, and I've had it on for thousands of miles with no deformation.
It's loud as heck, and I also wired in a toggle switch, mounted through the bottom of the headlight bucket, that I can switch between the stock *meep meep* horn and the new
WAAAHHN WAAAAHHN horn.
:headbang2:
-K