Take one of the brake covers off and look and see IF there is a nut on the inside of the bull pinion shaft. If it has that nut, you can have one of 2 things, you can have a tractor that had the early disk brakes from the factory or a tractor that had disk brakes installed by a dealer in the field. My brother in law lives at the southwest edge of Phoenix. When I go out there  I see more of the single front wheel tractors, here in the Midwest they are not too plentiful.