I did it. I put in an Isspro dual needle mechanical air gauge(one red, one white needle). The transducers are also the low pressure switches so you will need 2ea 1/8" NPT "T" fittings, two haldex 66PSI low brake air pressure switches and some poly oil pressure gauge install kits.(2ea 1/8NPT to 1/8 compression fittings and about 10' of poly line). Remove the transducers, and attach the T fittings, switches and line kits to the two ports where the transducers are located. run the poly line to the gauge or gauges as appropriate. A 1/8" NPT male, female, female street T is perfect for this.
You will have to identify which wire of the two on each transducer is for the low air alarm(ign on connect to ground, buzzer will sound), and that will get connected to one terminal on each new front and rear low brake air switch respectively. You will need to make a Y harness to connect the other terminal on the switches to ground to complete the circuit and sound buzzer/dash lights when the pressure drops below 66PSI. insulate and tape the unused gauge wire back into the harness...
I can take a pic of mine later when I get home.