Reverse wire location 84 Lesabre

Need to find reverse wire to hook up reverse control wire on aftermarket double din head unit for camera. 84 Lesabre limited,COLOR AND LOCATION WILL BE APPRECIATED! Hoping someone knows of fuse box or under dash location and color There is a black and a white to the reverse bulb socket don't know which one has power.  

Im not sure if the 80-90 models are the same as the 77-79's but if they are the wire for the backup switch is light green and dark blue. Dark blue is power before the switch so light green would be the wire you need, if you have a test light, try it from there. If you dont see those colors, then look for the white wire(since you said the wire is white at the bulb) going from the safety switch on the steering column. The white one is positive and black is negative at the bulbs.