On the 1966 Full Size Car, you could have had console stereo Multiplex with either a Caprice or Impala SS. The determining factor was the gauge package. In the Caprice, if you ordered RPO A51 it included bucket seats and gauges along with lower dash pads. In the SS bucket seats were standard so you ordered the D59 gauge package which again included the lower padded dash. The gauges mounted in the same place the standard multiplex would have installed, hence the console mount fo these models with the gauge package.
I am in the process of having the Multiplex Decal reproduced, should be done in a few weeks.
Paul