I assumed he was talking about the 09+ since the 08 and older wheels are ugly.The 2004 to 2008 CTS-V has a 6 bolt pattern.
That said the old CTS-V 6 bolt pattern is 6x4.53 or 115mm
The tbss has a 6x5 or 127mm
Ths STS-C has a 6x4.5 or 115mm
There is the info im leaning toward they wont fit even though they are 6 lug.