Here are PDFs of the Factory Service Manuals for various years and wiring diagrams.

XenonS130 - S130 Reference

If you're going to cut the harness and reconnect, you really don't need a wiring diagram. With a voltmeter and a 9 volt battery you can figure out the wiring in 10 minutes or less.

After cutting the wires, turn the ignition on, and use the voltmeter to determine which wire has 12V on it, your power feed. Next turn the headlights on and see if any other wire gets power, as that controls the dimmer in the headunit.

Connect the 9V battery across what APPEAR to be speaker wires, you'll hear a click or pop from the speaker so connected. So you can identify which wire goes to what speaker without blowing it out.

The only hard one is going to be identifying the power antenna wire because you don't want to apply 12V to any and every wire. If you do find a likely suspect you want to test with 12V, put a 1 amp fuse inline --- so if you're wrong, you only blow the fuse.

Undoubtedly MANY of the wires are the same for the non-GL, so start with a wiring diagram out of a 1983 factory service manual, or download a wiring diagram from Xenon's page and look for commonality.

Does the GL have one of those "Joystick" fader/balance controls? You may have to live without that.

I suggest you make a list of all the wires / wire colors and knock them out one at a time, and perhaps post it here to help the NEXT guy doing this job.

Ditto that post, except I use a 1 1/2 volt battery, it just makes the speaker hum a little so you can identify. identifying the 12 volt key, 12 volt light and 12 volt constant on Is just checking the wires one at a time, should be a ground wire there too. not sure about the power antenna wire. make a diagram, good luck!

The radio is already on the work table. I have the 8 pin (speaker) harness figured out. I have no clue what to do with the 5 pin connector wires. The diagram only shows 2 of them. I'll be more specific. I got a black wire, a green wire, a green/yellow wire, a red wire with a white stripe, and a blue wire. Also, trying to keep power antenna switch, but this looks like three wire harness which can stay. THANKS in advance for any advice you can provide!!