With my 2002, I got a Bluetooth/FM transmitter that sends the Bluetooth signal from your phone to the radio station you're tuned to on the car. It just plugs into the cigarette lighter. You just have to set the device to an unused radio station in your area. I also know that they make Bluetooth transmitters for the cassette tape player but I'm not sure how well it works. I'll link one of each.
FM Transmitter
A bunch of different FM Transmitters (basically just different styling of the same product)
Cassette Transmitter
