Peterbilt 387 Interface Module Location?

Does anyone where interface module is installed on 2007 Peterbilt 387? The interface module is what controls all of the guages like the air pressure, and air restriction guage. (I checked behind the dash panel, and behind the glove box, and could not find it.)

I am trying to install an air weigh scale on the truck, and the truck already has a "Load Pressure Gauge" installed. I took the dash apart, but there was no air line connected behind the "Load Pressure Gauge". I called Air Weigh, and they said I need to find the interface module. (If someone has installed an air weigh on a 387, please let me know.) Thanks.

 

Any idea where exactly under the Cab, the transducer is located. I was thinking about just extending the air line going to the transducer, and running it to inside the dash? Thanks.