[aerohead]

The 1964 Shelby Cobra Daytona Coupe, by Pete Brock also has a provision to 'duct' rear wheel-well air into the wake, ala John Simonson's 1953 Studebaker technology.
A photograph of the 'Coupe' was taken at Riverside Raceway during tuft-testing and shakedowns by Ken Miles.
You can clearly see the opening from looking back on the car.
All photographs of it's transom reveal blank-off plates installed, sealing off the openings.
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And it is the 2010 Ferrari 599XX which sported the dual-fan, blown-wake.
A 'permeable' central diffuser panel was exposed to fan suction, with the air cyclically discharged in controlled bursts, by piezoelectric diaphragms, through vacant taillight openings, to detach the wake.
The 599's Cd was estimated at 0.40 by a-c.
The car developed 617-pounds down-force @ 124-mph.
1,380-pounds @ 186-mph.
The tricks were referred to as 'universally illegal active aero.'
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Not to compare the 1961 Ferrari 250 GT to the 599, but Pininfarina measured a negative-34 at the diffuser location, to a negative-9 at the taillights on the GT, indicating that external power WOULD be necessary to move the air, otherwise the air would flow forwards.