I recently had to replace a radiator, and I bought the all aluminum one from fleabay, it has a thicker core. Why because I hate plastic parts.
I noticed on my 92 with external oil cooler, that it ran cooler. I was going to convert it to the slim line fans, but didn't see the need.
I agree that if it is only on climbing, then that is the issue as the engine is working harder, I usually saw this on my 81 regular diesel when I was climbing
Mt Eagle, or the rise from the Mississippi/Ohio river to the plateau of Illinois (steep climb there). Now it wasn't a turbo Diesel, but my car was loaded down with people, and clothes from visiting Grandma in Ala. I made that trip often, and after I had blown a OEM radiator (because of the crappy oem mounting) I opted for a Brass and copper one that served me well for over 20 years before I sold the car but on climbing I too noticed the temp rise, never to boiling but it hovered right at the line until the free-wheeling downhill....
P.S. I moved this to the Older Rabbit Forum...