1965 Formula S w/AC: What is Factory Correct Fan?

I think (not sure) the four-blade fans were used on the slant six motors. Here is a foto of the six-blade fan currently on my '65 Signet convertible (no a/c, no p/s, no p/b).

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I have seen the 4 blade ones on 273 2bbl motors and my 65 factory Commando 273 has a 4 blade fan.