On Board Air and In Cab Guage, Firewall hole needed

OK so today I mounted the Klein on board air system, I am not using train horns and only want the system for inflating after off roading and inflating other things so the compressor will not run all the time just off one of the switches. So my question is this thing comes with a pressure gauge and on my chevy 3500 I ran the gauge and mounted it in the Cab does anyone know of a small hole from through the fire wall to thread the small air hose?

You should be able to run it through a grommet in the steering shaft area.