Also,
What are the core dimension's H & W?
How big is the fan?
What is the distance between the shroud opening and tips of the fan blade?
When the engine is idling will it hold a shop or paper towel to the front of the radiator?
Will it do so across all areas of the radiator?
I would start with the above

Lastly, putting a fan in front of the radiator is not recommended as it can block the air flow at higher speeds

With electric fans, one normally gets what they pay for and CFM ratings are typically skewed especially on the cheap ones.
There are a number of sources depending on the room available.
Also, the higher CFM fans will draw more current so the charging system and wiring HAVE to be in good shape and sized appropriately