22” or 26” Champion ? Can’t decide

If your concern is having to cut the front opening larger for a 26", I think people worry too much about that. Air isn't light rays and doesn't have to flow thru in a straight line. It will spread out to flow thru the whole radiator, perhaps not as evenly, but close enough. Particularly true at idle when the fan is pulling it thru, and which is where overheating most commonly occurs. Many B-body radiators are too tall for an A-body. Some people have cut and peeled down the lower radiator support so the hood would close, but such hacks are ...