Rich,
I have to agree with Andras on this one and although I don't think that you have to stay with stock, the most important thing should be the quality (fit and finish) so I would go with the used factory turbo tail if you can . I have seen some "So-So" reproductions of the turbo tail and even have a "So-So" tt on my car now
It will eventually be replaced by an extended GT-2 wing
When that time comes though, I will be looking for a quality product (read as not cheap) just like you.
Good luck!
s