I've done a bunch of experimenting with powerful computer fans when there is a restriction like a radiator either in front of or behind the fan blades, moving the fan orientation when at speed to push against or pull from a restriction, like a radiator, or Ac condenser.
Almost every fan is not only quieter, but moves more air, when it is a pusher fan.
in the case of pushing or pulling, either works better the farther from the blades the impeller is, but a puller fan placed too close to the radiator just seems to stall the blades, the fan speeds up, makes lots more noise and moves a fraction of the air, compared to it it were just a little bit further away from the restriction.
A bigger fan is not necessarily more effective.
More rpm usually is more effective as long as the airfoil blades are not stalled from too much resistance.
CFM ratings are very misleading. They are taken my measuring velocity of air moved, when there is NO restriction to flow, then doing some math with fan diameter and coming up with some magic number designed to impress. The first problem with this is the velocity measured, it likely just to one side of one of the hub supports, where the air is accelerated around the obstacle.
Obviously a fan in front of or behind a radiator is restricted, so a fan designed for super high CFM, could perform much worse than one with a higher static pressure rating in such an application, and one with a huge static pressure rating in free air will seem to be underperforming, in comparison to teh high CFM fan, when there is no restriction to flow.
A high static pressure fan impeller usually has forward jutting, scythe like wider blades with a lesser angle of attack. High CFM blades are usually straighter, more numerous and angled steeper. Most fans are somewhere inbetween, but high pressure and high CFM can be a sweet spot of RPM and blade design with the amount of resistance and the distance from teh resistance all being huge factors in the overall efficacy. The CFM ratings should be viewed suspiciously, as should the amp ratings
The amp rating of a fan might be what the fan uses at 12vdc, it might also just be the start up surge. I've seen both, and do not trust any published rating until I confirm it, not only at 12v, but at 14.8v too as I tend to overwire for minimal voltage drop. I see far more fan's ratings correspond to their start up surge, rather then their draw at a steady 12v once already spinning but have not tested many radiator brushed motor fans. So I could easily be wrong.
You seem to be looking for an excuse to use the fan you already have, hoping it does something, but not really sure if it is needed or would do anything but make the alternator work harder and make more noise in the process. Each 25 amps the alternator has to produce eats up about 1HP, as alternators are only about 55% efficient and there are pulley and belt and Diode losses as well.
1HP=745.7 watts. 25 amps at 14 volts is 350 watts. Adding an actual 20 amp fan can simply add to the heat load for the radiator to remove. If the fan blades are stalled from too close a location to the restriction, then one cannot expect more cooling. So just slapping a fan on is no guarantee of anything other than time consumed.
if the cooling is questionable and it is confirmed to be running too hot, I like the radiator for the V8 idea the best.
Also, If the engine has a computer, it is expecting its thermostat to be OEM temp. A cooler T stat will likely just kill MPG and could be a short lived solution to running too hot. If the radiator or the fans on it are not performing as they should, a cooler t stat would just take slightly longer for it to run too hot, as the if overheating both a 165 or 1 195 t stat would be fully open, the 165 would just begin opening sooner.
Be very careful when powering unmounted fans, but in some applications, it is the best way to find out the ideal location/orientation in which to mount them, or decide against doing so all together.
