When you have never seen a light switch arrangement like that it can be a challenge to figure what has to happen to turn the lights on. Of the retired military trucks we use in the fire department, I think only one, an M35 we converted into a brush truck has those switches. None of the guys could figure out how to turn on the lights because nothing was labeled. The M1008’s we use as brush trucks are like hopping into any other Chevy except for 24 volts to start (everything else is 12 volt).