I would get a 2.5R best motor traxxas makes IMO.Your not gonna find anything better for the hundred or so it would cost you with the exchange.I just installed a Orion Wasp 18 in my rc10 gt and it rips really well but was a little pricey.On a side note going with the 2.5R or any other 18 might cause tranny issues from the added torque so be prepared.