I am in AZ with ya, and have a champion in my 84 K5 blazer and my sister's 2004 Escalade EXT...but for my 2007 Yukon, I went with a Cold Case radiator. They run the wider tubes like the Mish and the Be Cool...but at a smaller price than those options. Fully welded aluminum and priced below $400. Install of course does require some trimming of the brackets (in my experience, all aftermarket aluminum radiators do...to some extent) and trimming on the electric fan shroud since the one I purchased was a thicker core than stock...but a few thousand miles on it now and no leaks. Installed in the dead of 115-116 summer and even during engine break-in it worked very well.
Now, I don't do slow rock climbing but I did have to sit in traffic in those temps to/from work and such. Not exactly the same type of activity...but this is what I can report on. https://www.coldcaseradiators.com/ Also, I am not affiliated with this company in any way. I just hate the concept of a plastic tank molded to an aluminum core...a problem waiting to happen and I feel a solid solution is better, if I'm going to bother spending the time to replace anything.
YMMV
Now, I don't do slow rock climbing but I did have to sit in traffic in those temps to/from work and such. Not exactly the same type of activity...but this is what I can report on. https://www.coldcaseradiators.com/ Also, I am not affiliated with this company in any way. I just hate the concept of a plastic tank molded to an aluminum core...a problem waiting to happen and I feel a solid solution is better, if I'm going to bother spending the time to replace anything.
YMMV