Vortec 6.2L V8 SPI VVT High-Output, 6-Speed Automatic HD Electronic with Overdrive, AWD, CLEAN CARFAX!, LEATHER!, LOCAL TRADE!, And SHEEHY SELECT 125 POINT INSPECTION!. You don't have to worry about depreciation on this beautiful 2008 GMC Sierra 1500! The guy before you got it all! What a guy! This Sierra Denali is powered by the 6.2L V-8, generating an astounding 403hp and 417lb-ft of torque, which garnered it the title as the most powerful light-duty truck on the market. Consumer Guide Recommended Large Pickup.