Sierra 1500 SLE. Extended Cab. Vortec 5.3L V8 SFI VVT Flex Fuel. and Automatic. Extended Cab! At Yates Buick GMC. YOU'RE #1! Extremely clean 2011 GMC Sierra 1500. garage-kept appearance. with a Vortec 5.3L V8 SFI VVT Flex Fuel. The interior is in pristine condition and is very. very clean. Must see to be appreciated! This truck has been meticulously cared for. inside and out. It runs perfect. looking like is was always properly maintained and garaged. The Sierra 1500 scored the top rating in the IIHS frontal offset test....