The single wire you were holding with your left hand is either the heater motor lead which plugs in under the top passenger fender near the hood hinge. Its tough to see but if you get your head down into the engine compartment and look up into the top area of the front fender and the firewall, you will see a lead post sticking out for the heater motor. The 2nf thing it could be is the kickdown solenoid on the rear of the transmission passenger side above the cross-member.
How did the HEI conversion work for you? Did you go the Pertronix route?
