Yes,
it has definetely been done a couple of times (at least with a PT, but the effort maybe well the same). I would point you to the following addresses:
www.audifans.com => Audi V8 mailing list. There maybe a photo story as well on that page.
forum.group44.de => Unfortunately German, but there are some guys who have done this as well, even including a compressor and/or turbocharger tuning.
Possible is everything, but honestly: In your case I would head for a cheap 3B and put it back in place. When tuning it a bit (even though I won't) you get 300PS+ out of it easily leaving most standard V8s just behind you. And the 3B engine becomes rarer each day, AND you keep it in original state.
Regards
Bastian