Actually just read the new Motortrend on a flight home and they compared the GT500s against a Z51 C8 at VIR.
They directly compared the GT500 and C8 Z51 because that was a "closer comparison," and on the back straight it looks like the GT500 did 166.5 and the vette did 153.6. Not really a shocker there. Said and done, after putting the vette in "track mode" (basically just dialing in more negative camber front and rear) the times were as follows:
My opinion is for the GT500 vs ZL1 1LE (650hp) not the C8 Corvette (495hp).