The MT version uses a 14t pinion with a 64t spur I have seen kits for 13t,14t,15t with 53t,54t spur so I would expect there to be clearance to get that 13t to 54t. I would think you will want to go the 64t spur route with a 13t pinion with that motor.
Might also want to consider http://cgi.ebay.co.uk/HSP-1-10-RC-Car-Gear-Cover-Shelter-Part-03401-/180511734617?pt=AU_Toys_Hobbies_Radio_Controlled_Vehicles&hash=item2a07567b59 to protect the spur and pinion.
Also there is a hsp steel 64t spur that should work, but i havent tried one yet as i still not stripped the plastic original one yet. lol.
http://cgi.ebay.co.u...=item2a07567c0a
hope that helps