British Heritage has been doing this sort of thing for a number of years. They started with a complete MGB body, and have now moved onto another marque I believe. I'm waiting for them to do a Sunbeam Tiger/Alpine, THEN I'll buy in ! ! !
Although the MGB doesn't really bring in much money in restored condition, the bodies have done well as re-bodies for MGBV8's and the like.
Kind of bad timing with metal prices soaring and all. If you can make your price break and it's realistic AND you can get a "name" in the 356 community to endorse the final product, you'll sell some for sure.
BUT . . . the Porsche Boys are the pickiest, snobbiest, mostly nastiest, little runts that you'll every come across in your whole life. Be prepared, it'll have to be PERFECT in every way!