Thank you gentlemen!
From Le Man's picture it seems the fans are located inside the monocoque. The air comes in through the wheelarch opening and exits at the bottom floor level.
Hurstg01's photo displays what I believe is a duct for the alternator cooling, and confirms the lack of space in this area. It comforts me with the idea that the fans are situated in the flanks.
While the output of the "fan" used on the Chaparral 2J was +55 hp, I would be curious to know the total output of the fans used on the F1. Obvisouly it will be nowhere near 55 hp, but it would be interesting to know.