Any version of GSP that we have seen in the Octagon destroys Conor. GSP is just too good on the ground and that is a big weakness of Conor. GSP might even finish him in the championship rounds where Conor is likely to be completely gassed from the pressure GSP puts on him.
The only way I see Conor winning is with an early KO.
I don't think Conor has enough KO power for GSP. He clobbered Aldo, sure, but that's a 30-40 lb smaller man.