I probably had a combination of things on mine I had removed from old trucks I sold, but this kit is does it all:
I originally didn't have a gauge. I had the compressor up in the pin box itself (mounts right to the wood flooring up there and powered it from the pin box electrical (battery charge wire). The kit has tubing with the 90 degree elbow and fitting that goes to your shraeder valve on top of the bag.
I took the momentary switch and deflator valve and installed them near where my docking light switch was so I could operate them without leaning over the dually fender.
Later on I found the gauge and added it and installed an air chuck and momentary switch to turn on the guage light, but none of that is needed.
Ultimately, the Wireless One would have been how I would do it next time, as it allows me to adjust from truck cab and maintains pressure at my setting. With my set up if you wanted to adjust it you had to jump out. I always the wireless one would work great on air springs too.