Radiator recommendation for my 410 stroker

I do have room for a 26", I just figured that if I'm changing I would want to get the best. I would hate to go to a 26" and still be having problems and having to go to a dual pass in the end. I talked to a couple rad shops and manufacturers today and they basically said the same as you. I think I'm going with the 3 core champion. I have room for the 4 core but sounds like they can actually be more restrictive air flow wise.
I recommend talking to Wizard cooling and highly suggest the 2 core with the optional 1.25" core thickness. It cools my 570 hp small block with zero issues and is a 22" as well so no modifying needed.