Yeah, it's not that simple. Not at all.
Your anecdotal evidence about "cars that overheat under yellow" gives 4 different variables, any ONE of which could be the source of their overheating issue. And for many of them, it probably isn't the radiator at all. Because here's the thing, cars that overheat when sitting still usually have a fan problem, not a radiator problem. If they're staying cool at speed their radiator is fine, they're not moving enough air through the radiator sitting still. And of course, using a race car example is usually a bad choice, because people do really specific things that work well for their type of racing that will not hold up for a street driven car anyway.
The problem is that none of the aftermarket radiator companies, or the factory ones for that matter, publish enough of their specs to do a full mathematical calculation on them. This is on purpose.
A radiator is just ONE part of the whole cooling system. The water pump, the pulley ratio's, the CFM of air the fans can flow, the rate of coolant circulation, horsepower of the engine, ALL of that matters. If you look at the factory cars you see Ma Mopar had two major configurations, AC and non-AC. The non-AC cars got a .95:1 water pump pulley ratio (technically under driven!) and the HD 8 vane water pump (and usually a 2 core radiator). The AC cars got a 1.3 or 1.4:1 water pump pulley ratio, the standard 6 vane water pump, and a 2 or 3 core radiator depending on the engine, year, model, etc. Why did they change the water pump? Wouldn't more water flow be better for the AC cars that needed more cooling? Well, they wanted to increase the air circulation and keep the water circulation closer to the same. Overdriving the water pump was to speed up the fan, to move more air. But they downgraded the water pump, to keep that rate similar as the other set up. Almost like there was an ideal water circulation rate for that system and pump.
It's a cooling system, and you can't have a "properly engineered" radiator unless it was engineered specifically for all of the specifications of that particular car. Since we don't have unlimited ability to select pulley ratios, water pump output volumes, fan CFM etc there's gonna be a limit to what works well. And the "biggest two core radiator" that will fit isn't the only answer. Or even necessarily the right answer.
I run a 3 core with Ford Contour electric fans. Has worked great for me, even stuck in traffic in 110°F weather. I wouldn't trade it for a 2 core just because someone says bigger tubes are better.
Fan CFM has to be matched to the rest of the system. If you replace a mechanical fan that has an output of 4,500 cfm with an electric fan, you're gonna need an electric fan that can pull 4,500 cfm or so if you want to have a decent chance at it working. It's not the fan stalling that's the issue, it's usually just a lack of output. People seem to have a habit of picking fans because they have a cool aftermarket name or cost a certain amount instead of picking them by the CFM they can move. There are plenty of really expensive aftermarket electric fans that don't move enough CFM for these cars.
