A bronco radiator needs a lot of power to pull enough air through it. Most modern cars that run an electric fan have a lot of surface area and a really thin core. Makes for a fairly light load on a fan. The Bronco is small and thick, take a strong fan.
Advertised CFM ratings are worthless. If all you are going to do is use it as a window fan in the bedroom it might mean something, but not for cooling an engine. Good cooling fans (like Spal who also makes many of the OEM fans) will rate there fans not only in airflow but pressure drop as well. That has to do with how well the fan can pull air through the core and not just more free air.
Those that have made an electric fan work typically use a fan from a production car. They are engineered for cooling, not to reach a price point for marketing. They also draw big amps. Upwards of 40A and spikes can be 70-80A on startup. In short, the stock charging system can't handle a cooling fan that is really capable of cooling the engine. So now the electric fan now needs a charging system upgrade. And it isn't just the alternator that can't keep up. The stock wiring can't handle a high amp alternator either, so wiring upgrades to handle the high amp alternator needed to run the electric cooling fans. And we have not even gotten to the control side of things, adding the temp sensor and relay(s). And they need to be good relays, lot of amps and you don't want them to fail.
Taking a step back, one of the best things out there is the front accessory drive off a 5.0 V8 Explorer. It has a fan designed to keep a V8 cool with air conditioning running in an SUV. It is compact enough that the fan isn't right up against the core. You get an upgraded alternator (still need to upgrade the charge wire). The clutched fan only cycles as needed. No relays, temperature probes.
