Are there any differnces between a Porsche carerra cup Porsche and GT3 class Porsche?

[SALEEN S7R]

I know I should probably know the answer to this, but I dont know 100%. Can anyone tell me if the cars we see in the Porsche Carerra cup are the same specifcation as those we see in the GT3 class of the British GT championship? The same question regarding the Ferrari 360 challenge cars, are they the same specifcation as the 360s we see in the GT3 class of the British GT championship? Power wise im aware they are pretty much equal, but I was just wondering if theres any differnce chasis wise etc. Thanks in advance.