Land Rover Las Vegas sells D5s with Johnson Rods and 285/50-20 tires and there's still plenty of room. When I get the Johnson Rods installed my plan is to install LT285/55-20 Nitto Terra Grappler G2s mounted on Redbourne 20" x 9.5" wheels (picture from Redbourne configuration page shows what my D5 will look like with the wheels). The LT285/55-20s have the same tread width as the 285/50-20s but the radius is 0.55" greater, which won't be a problem.
2017 Discovery HSE Td6, 5-Seat, Capability Package
2006 GMC Sierra 2500HD 6.6L Duramax Diesel 4x4