Another vote for a Cold Case radiator. My car is a 79 TA 403 with 2.41 gears. I was using the original 3 row copper/brass radiator that was cleaned out and leak checked by my local radiator shop. Original shroud and 7 blade fan setup with new standard duty fan clutch, water pump, hoses, etc. 180 degree t-stat. Around town it was fine. But on the highway at 70 mph with the a/c on, it would heat up to 220+ with the daytime temps in the 90's. I verified the temperature was correct with a laser thermometer. It wasn't boiling over, but still not good. If I slowed down or turned off the a/c the temps would start coming back down a bit. I bought a Cold Case radiator from Summit and installed it. 2 row, 1.25" flews. Of course you can buy it elsewhere, but Summit is local to me so I got it fast. I changed nothing but the radiator. Now the temps don't go over 190 no matter what! 180 most the time. One of the best purchases I've made. Beautiful polished aluminum, all TIG welded, and fits like a glove, just like the original. The tank is a little wider than the original 3 row radiator, so you need 4 core mounting pads, or trim your old ones.
https://www.summitracing.com/parts/rad-gpf18a