Are you sure you need the raise the trailer? I have put 225 75 16 tires on my trailer and have 5 in. of clearance. More important is make sure the wheels you are considering have the right off set or you will have a problem with the edge of the wheel well.
WBCCI 12156 AIR 3144 WACHUNG TAC NJ6
2004 Excursion 4x4
1991 34 ft. Excella +220,000 miles, new laminated flooring, new upholstery, new 3200 lbs axles