1999 freightliner jakes

I've got a 1999 freightliner short hood classic it's got a c12 cat in it and it doesnt have jakes but I'd like to put them on. Does anyone know if the wiring is there for the switches in the cab? I see the wires under the valve covers tied up. I bought several of these trucks from a fleet and some have jakes some some don't and of course the one I'm going tom drive doesn't.

 

It doesn't have the jakes on it but the wires are under the valve covers. All of the c10s and c12s i have without jakes have the wires tied up under the valve covers. I also found 2 plug ins laying in the dash by the cruise control switches one has 3 wires and one has 2. I have the Jake brakes and housings off another c12 but I'm not sure what supplies the jakes with oil. It looks like they get supplied from the outer bolts that go through the rockers?