Radio Wiring

Not sure about an 84 but can't see why they would be different
as far as how they get to the back. The rear speaker wires run from the
radio down into the wire loom that runs through the console and they
exit the wireloom behind the little "glove" compartment and on the
cars with sail panel speakers, not in-seat speakers, they run behind the
firewall carpet over to the speakers. According to Haynes manual,
the speaker leads are:

Left Rear-Yellow/Brown
Right Rear-Blue/Blue
Left Front-Grey/Tan
Right Front-Green/Lt Green

I know this doesn't help much with the in-seat speakers but by
sliding the seat all the way forward, maybe you can see where the speaker
leads come into the seat. You might have to take out the seat - I dunno, I
never had any with in-seat speakers. The Haynes manual doesn't say
anything about them so don't know if they're wired separately or
running in parallel from the radio.