Really?? I find that interesting. Both your car and @LocuMob
's Monaco might be special order in that regard, and it seems odd that anyone would conciously choose to have diminished cooling capacity on such a car, when the factory deemed it necessary to do the upgrade to 26".
So, I guess it must have been possible to get a 22" rad on an AC car with a B or RB engine in 66, but I've never seen one so equipped. I could be wrong. Ya learn something every day!!
I know it's not a mid-production year change either, as my 66 T&C is a very very early ordered car, and it's got the 26" rad with AC.
I think that dealer installed AC (still considered "factory" by some) would have the car retaining the 22" rad, and would just add the shroud and clutch fan and 7 blade fan plus all the other engine bay AC parts (pulleys, adaptors, compressor etc.), and the evap and controls were hung under the dash. I had one once - a nice big Chrysler Airtemp knee knocker.
65 indash AC cars still had 22" rads FWIW.