That Engineered Cooling Product aluminum radiator is the one I installed a couple years ago in my daily driver CST/10 with a 350 engine. It came with a 15 PSI radiator cap. It works well and I have not had problems. I also installed this zinc anode in the radiator in place of the drain petcock
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
I use 2/3 Prestone concentrate coolant (undiluted ethylene glycol type) and 1/3 water.
I installed an overflow container. The overflow container allows the radiator to operate with no air in the system at all. All of the air is automatically burped out. I prefer that so there is no excess oxygen in there to promote corrosion. With my 2/3 coolant mixture, there is no expansion or boiling of the coolant, and the level of fluid in the overflow container does not change when the engine is hot or cold.