From http://www.classiczcars.com/topic/3291-request-advise-on-radio-installation/
My guess would be W/B for speakers, B/G for ground, G/W for power and L/R for illumination? You also need to work out whether the left and right refer to the front of the connector or the back. If it was me, I'd open the radio up and follow the wires/traces inside to work it out.