[SuperB70]

Here is my .02, been building custom cooling systems years. I think 8 now.

Core: its not about rows anymore, thats old scool when there only was one type of tube.

Nowdays tubes comes in many width and height. Even with inside tube fins. Most important is fpi (fin per inch), talking about airflow fins between the tubes. That is industrial scale of efficiency.
Ofcourse adding rows can make a difference means of coolant capasity.
But usually I can get by with 66mm core to first 1000hp at street car.
I choose to build horizontal flow cores, dual-pass. Not a big fan of original style vertical single pass cores. With dual pass design, I can control coolant flow better vs fan/-s.


Fan sensor: I go to local partstore and search/buy oem sensor with right turn on and turn off values.
In here (Finland) I use sensor for Volvo, has little lower turn off temp than on temp. There is two kind of sensors, ones that close the circuit and ones that earth it. I use mainly one that earth it. That controls a relay for the fan/-s or a controller. I can also connect a on/off switch to by pass the sensor if I want to run the fans what ever reasom.
LS and other modern cases ECU will control that.
I've come up a wirins system that uses 1 earthing sensor, 1x 4 pin relay, 1 or 2x5pin relays and a on/off switch. Then fan/-s can be contolled by temp sensor ( even when car is parked, ign. off) ECU or switch.

Fan sensor location: near upper hose or at least first 1/3 of the rad core height. If the sensor is lower down the line, the hole core get hot and takes longer to cool it. Can even be at intake manifold. Never in lower radhose, when thats hot, your rad has already soked the heat and you are

Fans: you cant go wrong with SPAL. If you want, you can get motorsport models, huge cfm but not Amps. With brushless motors. Not the cheapest, but there aint never cheap and good in same package. WRC rallycars, rallycross cars, track cars use them. Many high end supercars use them.

Fanshrout: I dont use those airflaps, not sure why anybody would use them. Fan opening is enough, just 3/4 off the core, seal it with rubber seal and fan/-s sucking hole area of the core. If one is running without the other. There need to be a blocking wall inside the shroud. Othervice the running fan suck the air from other fans opening and not through the core. Again first 1/3 of the heigth of the core is most critical, thats where the most heat is. I always try to amount AC and/or supercharger heat exchangers lower portion just because of that.

Thermostat: if you run without one, replace it with nascar-style restriction plate, just stainless steel "washer" with 3/4" opening. I use that even with electric pumps. And for those I use german-made Piersburgs out of BMW, cheap and flow the same as Davies but better pressure. PWM controlled either by ECU or stand alone controller.
Running with out any restriction means that coolant flows too fast and heat tranfer dosent happen. You gauge reads cool but engine can be boiling hot.

Coolant pressure: that is another friend of yours. Rises the boiling point, raise the pressure and boiling point rises with it. Make sure your core can handel that. You dont want that to turn in to football (american style, not soccer)

Expansion tank: if you have just a line from under the cap to ground. WRONG! You need to install a breatable tank with incoming from rad has inner tube going almost to the bottom. 1/2 or 3/4"short is fine. When the cap releases the pressure the coolant goes, like the name says expansion tank. When the coolant system cool after engine been shoot off, vacuum will refill the coolant system from the tank. How clever is that! Dont need to be refilling that 1"- 1 1/2" that is missing from rad.

Coolant: there is "new" style coolant in the market, no water, boiling point .Evans waterless coolant. Boiling point is 375'f

Oilcooler: Engine oil temp goes hand in hand with coolant temp. If oil temp is always up, you dont get coolant temp down. Hot engine is hot engine.
Good, powerful oil cooler with thermostat is good investment.

Airflow: you are in right track. There needs to be high pressure area in front of the radiator. Air needs to be forced through the core. When you need more cooling power, more fpi (fin per inch) you will need and that develops restriction to the air flow. You need to win that restriction. High pressure is you friend on that. If you have holes in radiator support, if air can go past the rad, no high pressure and you need to use fan/-s to make up for that.

Engine rpm: it plays a import role. Even in highway driving when throttle is at minimun if engine is turning rpm lets say above 3000 you will build alot of heat. That just is how gas engine work. Diesel needs fuel to make heat.

I build custom radiators, air to air intercoolers, air to water intercooler, heat exchangers and oil coolers from hand builded build to order european cores witch are all calculated for the orders spesifications..
So almost any size, almost any shape, even in a angle, width, length and thickness (factory determine that)
Anything from motorcycles, 100hp flathead, 3500hp drag and drive car, race cars to 120psi boosted pulling tractors.

As you can see in my project update posts of my 70 Coronet. Or more in my IG page.

But as of now I'm not shipping to US.