Factory look modern amenities most affordable option?

[dmjlambert]

Here is what I would do, but my disclaimer is I have not done it. I do use the Bluetooth module mentioned below to connect to the input of an under-seat amp and speakers.

Get a Bluetooth module that automatically switches from aux input to Bluetooth when a Bluetooth device is connected. This one has a relay. It routes Bluetooth sound from a paired device when the device is connected, via the out jack. It routes aux audio to the out jack when no Bluetooth device is connected.
https://www.amazon.com/Bluetooth-DRO.../dp/B07P94Z9XR

Power it by tapping off the grey wire that runs from inside the AM radio case toward the bulb holder in the back of the radio. That wire is turned on when the radio is turned on. I like to clean up the voltage with a voltage regulator.
https://www.amazon.com/Wolfwhoop-Con.../dp/B076P4C42B

Here is a thread where one forum member came up with an aux input connection for the radio, and several people did the project and also modified their radios. Cut the wire going to the volume control potentiometer in the radio. Connect the 2 each 2K resistors to combine the left and right sound output from the Bluetooth module to the high side of the volume control. Connect the left and right aux input to the radio audio from detector wire that was formerly connected to the volume control. The shield conductor from the out jack on the Bluetooth module should be connected to AM radio case ground. https://67-72chevytrucks.com/vboard/...d.php?t=502427

I suggest enclosing the Bluetooth module and regulator in a small plastic project box. Cut an aux cable in half to connect the wires inside the radio and allow plug in to the Bluetooth module aux and out jacks.
https://www.amazon.com/Amazon-Basics.../dp/B00NO73MUQ
https://www.amazon.com/Waterproof-El.../dp/B089K4KCQK

Should you decide to disconnect the Bluetooth module you can connect the plug ends of the aux and out into each other using a female to female adapter, to re-enable the AM radio to operate without the Bluetooth module. Or you can open the radio again and remove the extra wires and solder the radio audio from detector wire back to the volume control potentiometer.
https://www.amazon.com/dp/B01C9U3XI4/