Vortec 4.8L V8 SFI and 4-Speed Automatic with Overdrive. Wow! What a sweetheart! Nice truck! If you've been thirsting for just the right 2005 GMC Sierra 1500, well stop your search right here. This is the ultimate truck that is sure to fit your needs. The precision-tuned Vortec 4.8L V8 SFI engine provides the very essence of performance, delivering substantial horsepower and torque. J.D. Power and Associates gave the 2005 Sierra 1500 4 out of 5 Power Circles for Overall Initial Quality Design.