How to use a contemporary cassette & am/fm radio nowadays, to listen anything that you want, use bluetooth hands free with the car stereos own speakers, and fit to your old car without any ugly visible wirings.
No FM transmitter, No pendrive what you could easily break off, no 3,5mm Jack, and lighter socket...
Only the old head unit, and a small one touch Bloutooth reciever.

AM/FM DAB Tuner (RDS) - Pioneer KEH-P9700R (Top end head unit with DSP. Perfect quality sound)
Cassette player (Dolby Digital)
6/12 Multi CD (Audio) or minidisc changer - CDX-P25 CD Changer (or anything else, with IP-BUS connector)
AUX - anything what you want from your bloutooth device: MP3, WMA, WAV, OGG, M4A, AAC, video voice... - BT reciever, A cell phone / a notebook / Ipad / a music player... what has Bloutooth option.
Mobile phone conversation, or use voice recognition, to listen e-mails and masseges, to instruct your GPS mobile to lead you home...with only one touch - BT reciever, Cell phone
2 remote controller for the comfortable use. One for the steering wheel, and one system remote.

In car videos for example with Belkin, Ingadget, Parrot BT reciever:
   • Belkin AirCast Auto In-Car Bluetooth ...  
   • BMW 550i HTC streaming audio.wmv  
   • Ingadget - Bluetooth Audio Music Car ...  
   • Aluratek iStream Universal Bluetooth ...  
   • Add Bluetooth to amplifiers, receiver...  
...