Found a 2 page wiring diagram for a 64 Tempest here:
https://www.oldcarmanualproject.com/...re5765-340.jpg
https://www.oldcarmanualproject.com/...re5765-341.jpg
There does not seem to be a separate GTO diagram.
It shows an 8 pin connector as seen attached.
Dark Green goes to a rear stop/turn signal lamp. The diagram does not say which side, but I'm guessing left side.
Yellow goes to a rear stop/turn signal lamp. The diagram does not say which side, but I'm guessing right side.
One of the dark blue wires goes to a front turn signal. The diagram does not say which side, but I'm guessing left side.
The other dark blue wire goes to the dashboard turn signal indicator.
The natural wire comes from the stop light switch.
One of the light blue wires goes to a front turn signal. The diagram does not say which side, but I'm guessing right side.
The other light blue wire goes to the dashboard turn signal indicator.
The purple wire comes from the turn signal flasher.
The black wire comes from the horn relay.
The gray wire comes from the instrument panel lamp circuit to illuminate the automatic trans "what gear are you in" indicator on the steering column.
I ran across one error in the diagram where the Light Blue wire going to the right front turn signal suddenly became Light Black and then back to Light Blue. Most likely just a screw up by the guy that did the drawing.