My understanding of the radio options was that AM-FM would have been either U69 (mono) or U79 (stereo, 4 speakers - 2 in rear package tray and one in each kick panel). You could have also had U80 (2 rear speakers) with U69. If the kick panel speakers are factory originals, looks like your car has U79. If so, this would have included the multiplex amplifier, which was located under the passenger side dash, up above the glovebox liner.