Bone stock on the very heavily modified Corvette that is the ZR1, heh. Street tires and suspension settings though, thats the biggie.
I think when you get to this insane level of performance, you can't even really say the ZR-1 set a record, its their engineer Jim Mero who deserves the props for the time. The car we can just declare "capable of being extreeeeeeeeeeeeeeeeeeeeeeeeeeeeeemely fast!!!!" Cool to hear that GM has engineers that also happen to be race car drivers! If you gave the ZR1 to fifty different drivers though, you'd end up with fifty different times... some records, some not. Any of us here on the forum would likely suck in it, as it so far exceeds our skill levels!
Still, I bet magazine racers will find some other time two months from now that is .2 seconds faster with some other driver, and declare it the ueber winner.