The LS1 front brakes seem to be hit or miss whether they'll fit or not. Some have used the rear wheels on the front, some had no issues with the wheels fitting and some have used spacers to get the brakes to fit, The LS1 front brakes are probably the only larger brake upgrade that could fit the factory GTA's. pretty sure 4 pot calipers aren't gonna fit OEM GTA wheels, maybe the Hawks replica's? Scott at BBU would be a good source for some answers.
LS1 Front brakes and GTA Wheels ? - Third Generation F-Body Message Boards
LS1 brakes and GTA wheels - Third Generation F-Body Message Boards

 

I have the hawk wheels and standard C6 brakes are about as big as will fit.

 

Are the C6 calipers 6 piston? I’ve got 17x 9.5 ZO6’s and LS1 calipers, just curious how much bigger I could go.

 

No, they're your typical PBR dual piston, just much larger than the older 1LE calipers. I think the rotors are 12.8 or thereabouts.