Don't mean to hijack, but if you put a pusher propellor on a regular engine (ie, one that doesn't rotate backwards), it would push the plane? I had always thought the direction of the engine was necessary to accomplish that.
If you put a pusher prop on a "backwards" engine, you get a "pulling" engine again. If you have a twin with counter rotating engines, one prop will be a "pusher". Really, "pusher" and "tractor" props are mis-labeled. It would be better to call them "right hand" and "left hand", to tell what direction to turn them to produce thrust in a particular direction. But since all the moden model engines turn in the same direction, you can label them "pusher" and "tractor" and get away with it.