re: AM/FM Cassette and your cell phone Music
This can work, but with a bluetooth fm transmitter, not native in the phone, but I'll look some more.
Also the best type of device to add audio to a radio is the wired fm modulators. They tie into the antenna directly, no interference.
Something like this
I have used them in the past in several cars (not with bluetooth though, this was a while ago) and was very pleased. Audio quality is like a perfect FM signal, and that isn't too bad. Not CD quality, but who really needs that in an old car anyway.
1967 El Camino Malibu - Deepwater Blue
ZZ4 350, FiTech 600 complete!,Roadmaster tank, 700R4, Underdash A/C in progress, JGC Steering, 1990s truck serpentine.