The more I think about it, maybe a 46 would be best. That plane has a big fuselage, short wings, and a flat front. Plus it's twisted out of shape from so many crashes. If I even got it flying with a .40, I'm afraid I wouldn't have enough power to get out of trouble, like wind, or a bad approach. That junky KB 61 made me the king of dead-stick landings. It cut off all the time. I got so tired of fighting it.
But if I did dig up a smaller engine, I haven't a clue as to what propeller I'd need. Certainly don't want a nice valuable engine. Because the next time the plane crashes, I'm liable to walk away. It really is ragged out. That plane has been crashed so bad several times that putting it back together was a prolonged joke.