The Plymouth Superbird and Dodge Daytona had something similar on its' A pillars. ( That is the chrome piece that you can see in the picture :
http://aerowarriors.com/jpgs/88rd30.jpg
I found it interesting that they were removed when the car was run for top speed at Bonneville. Strange, since when raced on the speedways, they kept them on.
Bobby Isaac and his Dodge Daytona at Bonneville-1970 on Flickr - Photo Sharing!
( The above picture is a poor example, but I saw a better picture that clearly showed that there was no chrome deflector there. )
I wonder if the visor style extention did anything good at all for aero. :
Thanks for posting this question - I've wondered the same thing for years.