Engine Driven On Board Air from Kilby Enterprises
In the first picture you can see the two plumbing connections on the top of the compressor. There is an intake air filter on the suction side and the other goes to the coalescing filter.
You might also notice the small piece of rubber hose I zip tied to the rod that runs from the radiator to the firewall. That rod vibrated against the compressor with the engine running until I added this bit of rubber hose.
In the second picture you can see a Kilby air manifold with a pressure gauge and pressure switch installed. Behind the air gauge, you can see the smaller gray hose returning to the compressor from the coalescing filter.