EcoBill -
If I were to do a kit car I would *want* to make this work for me :
Perry Ds,Inc. 550 Spyder
It's designed to be bolted onto a stock VW Beetle chassis, so it's longer than the original Porsche 550 Spyder.
To make it more aero, I think you could come up with a low-slung hard-top for it. The 550 Spyder was raced with rear wheel skirts and a passenger seat cover :
CarloSW2