If you were only needing to inflate tires, there is a much easier way.
Mount an older piston style automobile A/C compressor on the truck motor. All the guys who run the sand at the beach do that.
No tank needed, just an electric pressure shutoff switch from a old compressor, a safety blowoff valve and then an air coupler all mounted to a T fitting. One step up would be to but an idle solenoid to raise the rpms when the pump clutch kicks in.
I still have one truck here with the setup on it and can put up a pic if anyone else is wanting one. I did run a tank on the first truck also...came in handy for other things besides tires.