Curious if there were any radiator cap clearance issues with the hood on the 26" radiator? Most of the 26" Mopar radiators that I've seen (Champion/ECP/Rad Express) have 23"+ height compared to 22" on the smaller radiators.
I didn't have any, but I have the earlier version of the 26" champion radiator, CC374. They updated it to a CC374B and I believe it got a little taller. My radiator is ~22 5/8" tall from the bottom to the top of the cap. At one point I used some silly putty to check the clearance on my hood and found that I have at least an inch of clearance to the cap. That's with a '71 Dart hood.
People have had clearance issues with the CC374B, although the model of the hood might have some influence on that, they don't all have the same clearance where the radiator sits. On my car anyway I would be able to run a radiator that was over 23" tall to the cap, I probably wouldn't buy anything taller than 23 1/2" though and shorter than that would be better.