For 3L carreras and turbo's there seem to be a shortage of tails.
Think it has been many years, that one could not buy new fibreglass tail, nor the rubber lip.
Jeff H.'s tail has no auxiliary grille hole, but it is easy to fabricate should someone want it for a 3L turbo restoration.
Auxiliary grille for US 3L turbo is still possible to find new, also it is relatively inexpensive ($200-300).
Of course there is always
http://forums.pelicanparts.com/porsche-911-technical-forum/527702-original-oem-tail-thread-collective-documentation.html
For part-numbers, consensus is you may find some, or not. I have two tails, one has the number, the other I have not managed to find.
A tell tale sign of a factory tail is, that it actually has steel frame around it, replicas likely to be all fiberglass. You can see the steel (iron) frame from this rough tail:
http://forums.pelicanparts.com/uploads16/75tail1266953278.jpg
http://forums.pelicanparts.com/uploads16/75tail11266953378.jpg
Try with a magnet, you will be surprised.