It been over four years since I added the Bluetooth adapter so bear with me! I think the old style cradle actually unclips from the base and then the adapter clips in in its place . The base should end up looking like the one in the link which then takes the Bluetooth .
http://www.350z-tech.com/forums/attachments/audio-electronics/43227d1211622979-350z-phone-cradle-question-cradle.png