Piston engine updraft and downdraft air intake systems, having a heat exchanger core and first and second intercooler flange structures having the same pattern of bolt apertures. The updraft air intake system has an air inlet component with an air inlet flange bolted to and having the same pattern of bolt apertures as the first intercooler flange structure, with the assembly configured to be mounted over the engine intake manifold with the air inlet component below the heat exchanger core. The downdraft air intake system has an air distribution tray with distribution channels, and an air passage closure tray that mates with the air distribution tray to form air conduits with outlet ports configured to be connected to cylinder air intake ports, and an air tray distribution flange bolted to and having the same pattern of bolt apertures as the second intercooler flange structure.