Here is a link to someone who races Ghias and has a little more input as to the aerodynamics of the Beetle and also Ghia.
http://www.shoptalkforums.com/viewtopic.php?t=115568
Barret Camper has a lot of racing experience and knows from that experience and trial and error.
I tend to agree with Volksdent that everything is a compromise, but with enough money and more importantly cojones, it can be made fast and quick, but I doubt that it would ever make it to 200mph or above
!!!
Take care and Happy New Years,
Kelly (Cohibra45)