To run a closed endbell motor like the Mabuchi you may have to trim the chassis a little bit (not totally sure).
I would have to agree with Corse-R. A 19-20, or even 17 would be a better choice: better efficiency for sure.
I don't know that I would go so much for speed as I would for runtime. AND WEAR GLOVES!!!! We did an enduro and everything gets REALLY HOT after awhile....