WB only makes (made?) three cylinder types: The LeRhone, the Pratt-Whitney, and the Gnome. The Gnome cylinders were only available in the larger 1/4 scale size. From my bried explorations of the web it seems like the Contiental witha a licence-built version of the Pratt-Whitney to that's the cylinder you'd want. The other two have that definite WWI look.