I did a few conversions that modernized old car radios. Aurora Design makes a neat little kit which removes all the old electronics, and replaces it with a well engineered small circuit board. The FMR-2.5 module will still use the tuning mechanism, and all knobs, so the old radio push buttons and knobs are still functional. I think this is a major plus for any purist that wants the look and functionality of their old radio.
Aurora also sells a Bluetooth module, which talks with the main FMR-2.5 module.
I have spoken with the engineer, and he's a hell of a nice guy. The FMR 2.5 module has a ton of features as he designed it to be universal with most every old school radio.
The Bad:
*You will most likely not be able to purchase these modules direct unless you become a dealer thru Aurora Design.
*If you do find a place to buy these modules, you will quickly find out that they are somewhat pricey.
*If Bluetooth is what you are after, you need to buy the main module and the Bluetooth module.
*You will need some skill level assembling this whole mess together, soldering is involved along with good reading abilities when following his manual.
*The heat sink that comes with the main module sucks, I had new custom heat sinks machined to maintain longevity of these modules.
*I'm embarrassed to say how many hours it took me to install this kit, labor intensive!
I was planning on providing a service on this site for this conversion, but the material cost and labor involved just didn't make much sense. Not many people here are willing to fork out 1k for a silly radio