The tank drain should be centered on the tank on the curb side of the tank and accessible without removing anything.
reach in behind the forward wheel and and you should fit it. I it is a 1/4 turn valve.
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