On my 01 I hung the compressor off the frame rail right behind the cab on the pass side and the tank from the rear bed cross member above the drive shaft in front of the spare tire mount. In both cases I used some 1 inch square stock that had predrilled holes in it every inch or so. Mounted the comp to to pieces then had two more pieces that I stuck on the opposite of the frame rails and sandwhiched the frame rail between them. This allowed me to stick the compressor up as high as possible. It was fairly well protected up that high but I also fabbed a box up to protect the comp out of some extra sheet aluminum I happen to have laying around. Worked great for 15 years until I took it off when I sold it. Recently bought a 2017 haven't got around to figuring the mounting on it yet but soon. If you only want the compressor for the horn then what you mention will probably work. However if you ever want to fill your tires, trailer tires etc you will wish you spent more money on 100% duty cycle unit.
I used an extremeaire from extreme outback. If I were going to buy a new one I would go with the magnumaire assuming I had the extra coin for it
https://www.extremeoutback.com/products/2/Air+Compressors.html