AC Wiring harness vs. Non-AC Wiring harness

"The a/c wiring under the hood for mine just involved adding a wire into one of the three plugs. Pretty easy. Classic or year one sells the under hood harness pretty cheap. I bought one for mine. Make sure you grease up the bulkhead connectors before remating them."

Make sure you use Di-electric grease. You can get it at any good parts store and it will both not react with the plastic in the connectors and won't conduct electricity so it won't short between wires.