Fastback rear speaker boxes

You can build a dirt cheap Bluetooth car stereo out of an old computer speaker set. Get one from Amazon or a thrift store that has a subwoofer. Get one that has a 12 volt wall brick. Ditch the wall brick & hook it up to 12v ignition power.

Buy a $20 Bluetooth converter with an aux output & plug it in to the speakers. Mount the speakers or wire in your own. Instant Bluetooth stereo from your phone. Cost maybe $40 -50. If you have an old pair of computer speakers hanging around like me, even cheaper.