When I first got my coupe I drove it from the thansport depot in Sydney to my home which was about 85 miles to the south. It ran on the verge of overheating all the way & was saved only by the fact that it was a cold day with a strong wind blowing straight at me & into the radiator with plenty bof light to medium rain.

I replaced the water pump & all related rubber parts. A check into the radiator revealed only six or so visible tubes, four of which were completely blocked.

I was going to replace the core with a heavy duty one, but one was not available at the time & was going to take too long to make, so I settled on a stock replacement.
Thanks to the cheesecloth condom filter, I have never had a moments cause for concern ever since, neither in summer heatwave or in recent sleet conditions.

Returning the whole cooling system to essentially new, & stock condition is always a good start & a heavy duty radiator is never a waste of money, just make sure that the thermostat is of a suitable heat range & is actually installed. [& not left on the bench]