Both. The 26” is better for cooling, surface area is king in thermodynamics. And the contour fan set up won’t fit a 22” radiator. I didn’t get the 26” for the contour fan set up though, I went with the 26” first because I had a factory 26” A-body radiator and added the mounting points when I converted from /6 to V8. It leaked so I replaced it with another 26”.
Champion just doesn’t list a 26” radiator for A-bodies. Not sure why, A-bodies came with 26” radiators from the factory. You just have to check the height dimensions. They’ve changed the measurements more than once since I bought mine. There’s also some new offerings for aluminum radiators now too, some with stamped tanks that look a little more factory.