I've got onto the habit of switching horn over when I hitch up, It's on my "pre-flight" checklist which CRS has required.
My horns, tank and compressor came as a kit. Mounted tank, which has compressor mounted on top, in truck bed behind wheel well. Can still use bed to load 4' X 8' sheets with no interference. Also mounted air chuck quick disconnect to bed rail and with 3 gal of 150 p.s.i. have no issue with airing tires. The compressore is high volume so if airing a large tire I just let truck idle so compressor will run.
The on board air is handy for the air bags as well. I have solenoids to air up and exhaust the air bags with redundant gauges and switches in the cab and at the rear of the truck bed where I can reach it with the tailgate up. With the rearview cameras it makes hitching and unhitching a breeze. The Husky Brute 4500 tongue jack with remote control helps to.
All of this to compensate for the 5 surgeries on the left arm/shoulder and 6 on the cervical spine.