You do have just one ignition switched power wire, it should be blue, but may be red. As you noted, it splits into several differnt wires at a factory splice, which is located in the main harness running across the bottom of the cowl. The splice is roughly above the left 'leg' of the bulkhead connector wiring, approximately half way between the brake booster and bulkhead connector. The splice into 4-5 wires was used to power the lean burn computer, one of teh alternator fields, and emissions accessories. If you no longer have need for all these wires, I suggest locating the factory splice, and clipping the un-needed wires at the splice. At the minimum, you will still need two of these wires from the splice, one for the alternator field, and one for whatever ignition you are running. If you have an electric choke, you will need a third wire from the splice to power it.
If you still have emissions items on the vehicle, you may still need ignition switched power for them as well. I do not have a wiring diagram in front of me, but EGR timer and bowl vent solnoids come to mind.
-S/6
