Here's the key post from RL:

"When I left in September we still had a myriad of PVS ("Produktionsvorserie" = Second to last prototypes before the "0-Serie") cars of the GT3 and they had everything...
Manual
Manual without wing (!)
PDK-S
3,8l engine
4,0l engine 
....

Even the "standard" engineers at my department did not know for sure what options they would offer in the end.
At one point it was "GT3 standard = Manual w/o wing" and the Clubsport package would include the wing and PDK-S

I think they killed the Non-Wing version though, but I wouldn't put my money on it.

4,2l engine what I read somewhere is bogus. Not possible with that engine block "safely".

I'd guess that they put the 4,0l engine from the RS with ~490hp (or even the same as RS/R with 500hp) in it."