There is a good pic of 318 on page 89 if Grandt's Narrow Gauge Pictorial II, which shows only one stovepipe at one end. The window arrangement suggests there is only one toilet also. It could have the stove at one end and twin toilets at the opposite end of the car like some of the other cars I've seen in Heimburger;s Narrow Gauge Plans book. Others may have more information...
Robert