seemed it was about time to find out why the rear speakers didn't work on '87 #2. PO swapped in an aftermarket cd player, and the front speakers work, along with all the other functions of the player/deck. first checked to see that there were speakers in the back, and there are. stock, in the stock rear location.
the install was something of a hack, although at least the PO didn't hack any (that i can find) of the original stereo wiring harness; just hacked the adapter harness. when using jumpers to the rear speakers from the deck wiring, no sound from the back. did a little google, and also remembered that the rear stock speakers have a small amp mounted at each of them.
much of the writeups are erroneous with regard to installing an aftermarket player into the system using the original front & rear speakers. on most new heads, there is a wire labeled "remote power", and most descriptions describe this as for an antenna. it isn't. it's used to power the remote amps, in this case the ones for the rear speakers. using the factory wiring from the amps, i was able to connect to the labeled "remote" wire lead, and.....the rear speakers work. so, after 3 years, i have music in the back, too.
the speakers in '87 #1 have always worked, as it came with the original deck, and i swapped in a later cd/deck from a similar vintage toyota. the deck had identical wiring plugs, etc, so everything worked.