I would advise against 20s. I work in the tire industry, 20" tires on light trucks have a rather short life expectancy. They also tend to agrivate any aligment issues, plus the extra weight puts exess strain on steering, suspension, and brake components. I would suggest something more in the line of a 17 or 18 max, and keep the width no more than 10.5" to prevent suspension and steering component contact issues.
