Ewwwww! <;~0
...When folks start talking of cooling issues,, I always mention to check and even calibrate the thermostat,,, 'simple-first'!!
I once had a brand new OEM thermo I installed in a new rebuild,, that didn't function! I consider it important to put the thermo in a pan of warm water, bring to a boil,, and confirm the temperature it's fully open... I believe that's meant to be 180degrees iirc. The cost of yer engine is well worth the price of a thermometer!

...On the Radiator,,, I believe you can get a 4 layer core in those.... more is better, in this case. <;~]