2 Pack 1/8" 3.5mm Jack Audio Cable to XH2.54 3 Pin Terminal Female to Male Plug 3 Pole Stereo Audio Cable Amplifier Extended Line

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.