Have a look at Pantera Place, it is a great source of information. Here is a link to the wiring in the technical section. http://www.panteraplace.com/page107.htm
I like this diagram, it is partially in color. http://www.panteraplace.com/El..._pantera_diagram.pdf
There are also diagrams in Pantera Place which just focus on individual sections.
a) Does the relay click or operate? You can swap the relay with say the ac condenser fan relay. Most likely the horn itself.
b) Depends where the oil temp gauge is located in the car. If in the center console use the pink wire that is on the other gauges. You could use this wire also if the gauge is in the dash.
c) Yellow/black should go to the rheostat for the gauges, with an orange supplying power via the light switch.
d) The blue supplies the power to the lighter which should be live all the time. The orange is for its illumination bulb. The pink wire could be from the parking brake switch.
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