Vortec 5.3L V8 SFI FlexFuel and 4-Speed Automatic with Overdrive. Extended Cab! Red and Ready! Are you interested in a simply great truck? Then take a look at this good-looking 2007 GMC Sierra 1500. It scored the top rating in the IIHS frontal offset test. It is nicely equipped with features such as Vortec 5.3L V8 SFI FlexFuel and 4-Speed Automatic with Overdrive. This outstanding Sierra 1500 is just waiting to bring the right owner lots of joy and happiness with years of trouble-free use.