Maybe this has been asked here before, but I can't find it, so...

I recently bought a 2001 Mustang that came equipped with the multiple cd changer radio. The CD doesn't work, so I'm planning on replacing it, and I want a combination cd/cassette player unit, but I don't know which one is interchangeable for a direct hook up. The number on my current radio is 1R3F-18C815-AD, and I need the number for the cd/cassette unit that will replace it. Can anyone help?

If not, could anyone suggest an aftermarket unit that will work and is still available? I've tried Crutchfield, and they don't have anything.

And before anyone suggests a used parts dealer (junk yard) that's what I need the proper model number for.