Squarebody Dually Fender Clearance Light Wiring

#1
I was preparing to do a simple blinker mod on my squarebody dually fender clearance lights until I exposed the wiring in the loom running to each fender.
I expected to find one hot wire and one ground wire. To my surprise, I find two brown wires and one black wire leading to the passenger fender and two brown and two black leading to the driver fender.
What the heck?

Dually Fender Wiring - Passenger Side.jpg Dually Fender Wiring - Driver Side 1.jpg