The orange wire is the power wire and has constant power to the dome light. It runs from the fuse panel to the headlight switch for tail light power and it also runs from the fuse panel to the stop light switch for the brakes. The power for the dome light runs from the fuse panel down under the drivers side sill plate and up to the dome light.
The white wire is the grounding side of the circuit and it runs from the headlight switch down to the harness to the drivers side door switch and under the sill plate back up to the dome light. There should be a junction with another white wire that runs over to the passenger side door switch as well.
Follow the orange wire at the light switch and the white wire is just below it.
Ignore any arrows they are for other stuff.
This is the orange wire feeds from the fuse panel, The large red wire feeds the orange wire which is fused and then feeds the brake switch, the headlight switch, and the dome light. These are not key on power.
This is the wiring to the dome light and the rear lighting. The fuel sender goes under the sill plate too but the tailight wires run under the truck cab along the frame.
