You seem determined to give as little information as possible and then only in response to direct questions. Why don't you just try the Mabuchi motors website (http://www.mabuchi-motor.co.jp/engli...uct/index.html) and see if you can find a motor which fits the mount, whatever size and shape it may be ?

BTW 6x3 is a fairly normal prop size for a 380/400 motor when used as a lift fan on a hovercraft. I usually use 7 cells though.

Steve