DROK Blue~Tooth Board, 12V Audio Receiver Blue~Tooth Module DC 5V-12V Portable Wire~Less Electronics Stereo Music Receive Circuit Chip with Micro USB Port for Headphone Speaker Home Sound System DIY

Okay this is going to be a quick ramble because I wanted to correct a few mistakes I made whenever trying to describe my ideas The Bluetooth board I bought converts it to an analog signal before amplification so we do not have to worry about digital signals (oops) so we should just be able to splice it in anywhere The signal is taken in for a specific audio input method preamplification (cd or cassette) https://a.co/d/0fFi5MtQ I'm also perfectly okay with losing all original functionality from that input

Okay this is going to be a quick ramble because I wanted to correct a few mistakes I made whenever trying to describe my ideas The Bluetooth board I bought converts it to an analog signal before amplification so we do not have to worry about digital signals (oops) so we should just be able to splice it in anywhere The signal is taken in for a specific audio input method preamplification (cd or cassette) https://a.co/d/0fFi5MtQ I'm also perfectly okay with losing all original functionality from that input

This. Get a BT audio board that can take 12V in like this. Get a 3P audio breakout cable like this. Take your 5 pins from the car: 12VDC goes to the power in terminal on the board GND goes to the ground terminal on the board The three wires from the 3.5MM jack of the car go to the 3 wires of the 3P breakout cable (Left/Right/Ground), just cut the female 3.5mm jack off and interface those end of the wires to the car If you put an "add a circuit" tap off a switched fuse on your car, you could do away with the jack/cable/micro usb adapter and tuck this all behind your dash.