"I do not know what electrical diagram is for a 1973(1/2)..."
Randy,
That could be SL35, the wiring diagram I haven't scanned and cleaned up yet. Many diagrams aren't labeled by model year. I count the number of fuse positions to ID the correct diagram. How many fuses in your car?
Sherwood
http://members.rennlist.org/911pcars
Correction: SL35 is there. I haven't done SL37 yet.