The Chevrolet will gain the six-speed automatic and.....drumrolll.......the 6.2L Vortec with 403 hp and 417 lb-ft and still get 19 on the highway. As for the 5.3, it will initially get the six-speed only in the crew cab but will trickle down to the regular and extended cab later on. With the 5.3, fuel economy for the 4WD is 14/20, quite good.