Electrical OEM stereo reinstall wiring help needed!

I know there have been a few posts on this in the past. But I'm hoping someone with more knowledge than me can help me figure out where to go next.
I went to reinstall the original radio on my 87 GT hatch. Upon doing so my fears were realized, the previous installer hacked up the original harness. My car originally came with the premium sound option. The original football amp is missing. They also installed new door speakers that it appears they ran new wire for and spliced into the post amp harness. I'm thinking if I can find the proper original style amp, and get another connector that is now missing that would go to the amp. Then I should be able to piece it back together?

My assumption is that the wires from the door speakers are no longer tied into the car harness. I believe these two wires to be running to the door speakers, and look as if they just tied them into the matching wires on the amp harness. If that makes sense?