Info on a prop size for a chainsaw might be hard to find. Not many people use chainsaw motors. Due to all the torque and HP of them though, I'd recommend a prop on the larger size used for a weed wacker motor. Sorry I can't give you any specifics.

Since it's a gasser, it's recomended that you get a high torque servo for the rudders.
A suggestion for the rudders http://www3.towerhobbies.com/cgi-bin...&I=LXDTB3&P=ML

And a Futaba S3003 or S3004 or equivalent will work fine for the throttle. Any servo will work fine for it really.