hi everyone!

i need help with the four wires i have going to the rear of my 62 chevy ice cream truck

i figured out three of the wires, but the fourth is needing some help

i have four wires to the rear

red= right
green= left
black/white tracer parking light

white=????????????????

I need reverse!!!!

the white wire emits from under the dash and is cut there, and it is coming out towards the rear of the stepvan.

i know this is a stepvan!! i just cant find any help with specific wiring

i know that this 62 chevy has a signal stat900 and 54 chevy truck guages and lights.

any help with this white wire would be great or even an idea would help.
thanks
jeff