Hello all-
Sorry about the delayed response. Holidays have everything in an uproar. Anyway, the wiring issue has been solved, thanks to all of your advice and help!
Here's what I discovered:
For the 1988 model, with premium sound/6 speakers, you need to order the wiring harnesses from crutchfield, making sure that it includes the amp bypass harness. The model I ordered was called: "Metra 70-5006".
I unplugged and removed stock radio by rigging two pieces of a wire coat hanger instead of buying the tool. I then removed the amp by unscrewing the two front facing bolts and sliding it forward. I unhooked both wiring harnesses and removed the amp.
Then, using the amp bypass connector (shaped more like a square than the others), I hooked it into the harness that once was connected to the amp. These I spliced to my speaker connectors on the radio harness.
Then, I connected the other harness provided (skinnier and more rectangle shaped) to the appropriate power connector that was once hooked to the stock radio, and spliced those to the appropriate wires on the radio.
After that, bam----sound in all speakers.
Thanks for all of your help! It was very much appreciated, and I got through this first trial! I'll be in more threads coming up as I slowly restore this car, so I'll see you guys around. Thanks again!