There is one of these listed on-line at a site called Auto-Buy. It is totally restored and there is a list of all the features listed. One of the features is a Becker Europa.

The dash speaker is clearly visible, but in the kick panels there appear to be speaker covers. I used to have a 6.3, so I know the A/C blower is behind the passenger kick panel, but this car looked to have a different type of A/C, more like one found in the 600.

The drivers side kick panel also had what looked like a speaker cover, so perhaps the blower is under the dash and the speakers went in the kick panels?

By the way... If you install two speakers to handle both channels then the middle speaker need not go to waste. You can connect the two (+) leads to the leads on the center speaker and pick up some sound that is otherwise lost.

Also, if you do install a stereo Becker then please remember that the balance, or fader, switch is not built into the radio. It is a device on its' own and will need to be installed as well. I have seen these both in the dash and in the console.

I figured you knew this, but someone else may read this years from now that does not.