Go with either an OS 46 AX or Thunder Tiger Pro 46. The plane is a bit on the heavy side and a low wing. With that combo its better to have a bit extra power than be on the weak side. The plane is an advanced trainer which will make a nice 2nd type plane when the speed brakes ext. are removed from the wing after your training. Therefore you are actually buying an engine for 2 planes at once so now is not the time to worry about saving $10./$15.00. You want an engine that is user friendly to operate, has good throttle response, strong running and strong reliability. An engine going deadstick on a P51 is not a good thing. Thats why I suggest one of these 2 engines. [8D]