We drove the Mercedes-Benz G 63 4×4 Squared the way it’s supposed to be driven: on-road and off. With 13.8 inches of ground clearance, three locking differentials, and 577 hp, this SUV is one of the most capable off-road vehicles in production today. It has a base price of $349,000 and it’s not available on the Mercedes website, so spotting one in…