Vic, I used to have a picture of the U80 rear speaker option in a convertible, but I can't seem to find it now. I'll keep looking and if I find it, I'll post it for you.
However in the meantime, if you ordered an AM radio, or an AM/FM mono radio, and also ordered the U80 option, you got one speaker on the rear passenger side of the car. If you ordered the AM/FM multiplex (stereo) and the U80 option, or the 8 track player (which automatically came with the U80 option), you got four speakers.
If you're looking to install the speaker(s), then check out
THIS THREAD. Pay close attention to what Mark Canning (Mark C) posted about half way down.
Ed