I'm not encouraging to do the same, but I have clocked in my Denali 139mph with GPS (the only way to know). With better conditions I would bet that it could do better (there was not enough road). It was late at night and had my Beltronics STI Radar Detector on (bad ass radar BTW). The truck has custom programming, intake, no cats and custom borla/pypes mufflers (one after another replacing OEM).
It did 14.6@98mph on the 1/4 mile with the engine hot as hell (didn't let it cool down) with 100k+ miles on the odometer. I love my Denali. This trucks are amazing... period.