You have a few choices for air hoses setups that I know of...
One: My M35A2C has a quick connect (standard air hose fitting) under the glove box in the cab. Fitting is plumbed in with a ball valve that is connected to the line on the firewall, so you have to open the valve to get air. The M35A2 that I have only has a plug in the valve and does not have a connector but I could always snag one and add it if needed.
Two: My M35A2C has a tee fitting just ahead of the large valve at the gladhand on the rear air line (passenger side of the truck) with a smaller ball valve and air line quick connect fitting that the USAF added when they had the truck in order to feed a regular air hose without having and adapter or having to disconnect a trailer.
Three: Use an air hose that has a glad hand on it and just connect it to the fitting on the back of the truck on the passenger side. I got a glad hand with a pretty long hose on it from Army Surplus Warehouse (other dealers and folks on Ebay have them as well) along with some other stuff once, but you can snag a gladhand at your local heavy truck shop or truckstop and add a hose...