sentences:  For the 1969 model year, the GMC F was replaced by the GMC Astro, while the Chevrolet Titan 90 was unveiled for the 1970 model year.The GMC Astro/Chevrolet Titan are Class 8 cabover-engine (COE) trucks, sold in both single and tandem rear axle configurations.In contrast to the Crackerbox, the cab of the Astro was lengthened nearly six inches into a 54-inch BBC length with two sleeper cab configurations available.