Audio Systems: 1969 Oldsmobile Delco Wonderbar, digital multimeter, infinite resistance

Question
We are putting the finishing touches on a 1971 Olds 442 restoration.  As I am not a purist (I am always looking to improve a design)I am installing a 1969 Wonderbar AM/FM radio in the car.  It did not take me long to know that I'm not sure how to hook it up.  Can you help, There are three inputs, but I'm not sure which one is the 12v.  Do you know where I can get a wiring schematic?

Answer
Here's an easy way to test your radio's wires. Measure with a digital multimeter from the case to each wire, with th evolume/power switch off and then on. The ground wire should always be a direct short. The power wire will go infinite resistance when off, and then some resistance when switched on. The illumination wire should always be the same reading. Most old GM stereos were grey for illumination, yellow for power, black for ground, and two green wires to the dash speaker.