I doubt factory installed, but dealer installed is possible. BUT, the compressor mounting setup on the 3.6 requires a modification of the engine wall. If the early engines are anything similar (I would think so because of the pulley/belt arrangement) it would require similar modification. It's still conceivable to me that a dealer would install AC on a 914/6 to make a sale.
But AC would only hurt the value IMHO, regardless of rarity.
Are you collecting 914/6s now?