We have a C or a pregnant B+, whatever you want to call it mounted on a Ford E450 chassis with the Firestone Airbags and on-board compressor. fortunately I didn't have to mount the stuff but perhaps the following will help.
The compressor, solenoids etc. are all mounted on a separate board and the board was then mounted in the rear compartment which houses the black and gray dump valves. this keeps it out of the way and out of the weather. Air lines were run from there to the two airbags and also up to the dashboard to supply the pressure gauge and controls.
2014 Triple E Regency GT24MB (Murphy Bed) with all the good stuff
towing a 2016 Jeep Cherokee TrailHawk
Berkley, the amazing camping cat missed dearly (1996-2012)