When I first saw phones modded with Bluetooth in them, I really wanted to make an antique phone bluetooth mod. In the summer of 2007 I came acrros a great deal on an antique phone reciever. I used the built in microphone on a motorola bluettoh headset, and wired the output to a headphone speaker. A year after I made this, I took out the Motorola headeset for plantronics one since it was easier for me to get to the leads for the buttons. I was then able to attach the headset to a pushbotton, and I manuevered the button into the phone assembly so that the phone revicer's buttons controls the on/off/pair button on the headset.
Contact me if you have any questions or want more pictures.
On of these days I'll make this page look pretty...