The holes on the 26" 3 core were easy enough to fix, couple of minutes with a drill. And to be fair, my Duster originally had a 22" radiator so I had to drill the holes and weld the backing nuts in place, so I might have been a touch off. That also only took a few minutes, and since I did it myself it was "free"
A-bodies DID come with 26" radiators, because that's where I got my original 26" radiator to drill the holes. It came from a '74 dart with a 318 and AC. It also had a larger opening in the radiator support. I can even post the fender tag. Unfortunately, I knocked a hole in it so I needed a replacement.
Brian you don't have to post the fender tag just to prove me wrong. If you read the way I worded it I said I had never seen one. I have not had any A-body that new so I didn't know it was an option.
As far as the 26" radiator not working correctly with the 22" opening, it's simply not true. Surface area is surface area, and more surface area means better cooling. True, it might not work as well as if the opening was 26". But it will STILL cool better than a 22" radiator. That extra fin area is still exposed to the air, and while it may not get more moving air, the ambient air temp is still cooler than the radiator. And given that I've had to change to a standard 195* thermostat to keep my engine at temperature, I would say it's working.
