Here's the link to the bluetooth deviceI purchased MakerHawk Mini Amplifier Board Bluetooth Amplifier 2.0 2X50W 5V-24V Audio Power Amplifier Module for Store Home Theater Speakers https://a.co/d/dewspZw
For anyone interested, it was an extremely easy fix. The device gets power from the original radio switch...so, my original radio turns on the bluetooth device.
Then, I hid the device inside the original radio, hooked the speaker up to it, and voila! Phone connects to the bluetooth, and now we're playing 1940s music through the original radio.
From start to finish, it took a hour or so...couldn't be happier with it.