RE: Building a wing like F40 from scratch. Need sp
Well supposing you can come across a piece of an asymmetrical airfoil that would be the ideal wing section, but it would also involve custom fiberglass so it's really a big can of worms to open. Now if you can do this yourself go for it otherwise I'd say just buy one from somewhere like Erebuni or (if you dare) Motorsport.
You might look at some ferrari enthusiast sites for inspiration as I don't think ferrari.com would still have F-40 pics up (then again they might so you may want to check)