I don't think that would work. If the narrower deck's gauge wheel bracket would set inboard enough to rub the tires, using a wheel spacer to move the rear tires out would only move the point of interference inboard on the tire. You would have to move the tire out it's full width (12"?) to solve the interference problem, or use a smaller diameter tire.I wonder if you were to install spacers between the axle hub and the wheel rim if that might alleviate the clearance issue? The only way to know would be to jack up the rear and remove the tires and rims and start taking measurements. Once again, we are headed down the road of modifications and who knows how Kubota will look at this should there ever be a warranty claim for the drive train.