1967 electric brake wiring

[phoney]

I'm having problems with the wiring on my electric brakes. My 1967 Overlander manual says the yellow wire on the umbi cord goes to the brakes. I found that at the splice under the front access cover. At the wheels there are 2 wires, a white and a black. Where does the second wire come into the picture and where do I find the ground to the frame? I have 2 wires at each wheel so I know there has to be splices under the floor pan.