I put the compressor inside the truck where the factory jack had been. I only needed two holes for the air lines, and thoes were covered with plumbers epoxy to keep everything water tight and secure. You could use some JB Weld to do the same thing.
Granites idea is the best if you don't mind removing your jack and extending the wiring. Obviously, the cabin air is cleaner and cooler then the dust and heat underhood. But, I havent had any issues and use it regularly on the ice patches on my driveway.
The back is what I was thinking since that's where the battery to run it will be. Don't mind removing the jack since I don't use it anyway. Just gotta put it into the plans for the storage unit.
Mine is mounted under the hood. Up high on the passenger side by the Cruise Control module. Lines are run down the frame rail and follow the brake lines down to the axle. Click the locker link in my sig. The only two pictures I have at current.
Most people don't use other systems as the fittings are rather odd thread. For example the tubing airline is metric. The fittings are strange british pipe thread. Conversion fittings are not the easiest or cheapest to locate. I gave thought to a onboard air setup but when the fittings cost nearly half the cost of a separate compressor just didn't make sense. Maybe they are available at lower cost now do not know.