How many feet is a GMC Sierra 1500? Base 4x4 Crew Cab 5.75 ft. box 147.4 in. WB. 2020 GMC Sierra 1500 Specs. How many miles does a GMC Sierra have? With good maintenance, a GMC Sierra can reach 150,000 miles, with many models reaching 200,000 miles. Surveys have shown that about 1.7% of the GMC Sierras on the road today will surpass the 200,000-mile marker. These vehicles don't require complex maintenance procedures. How big is the GMC Sierra 1500 Hybrid? See more GMC models and years. 2013 GMC Sierra 1500 Hybrid. The GMC counterpart to the Chevrolet Silverado, the...