The downside of using your phone for music & satnav is that it is illegal to do so whilst you are driving even to change music or directions. If you want to keep the retro feel, there are plenty of retro style car header units available nowdays with all the modern stuff like USB, Bluetooth etc and as far as i am aware, they are still ok to use whilst driving although not recommended. I have a proper 80s stereo in mine but connected to an amp with USB & jack plug mounted in the glove box. Not ideal as I need to keep the glovebox door open & will probably change but I wanted to keep the proper retro stereo.