If you drop in an .18 size motor find frost's thread on an aluminum clutch. The aluminum cltch is well worth it.

Right now, you would have everything to drop in an OS 12CVRX or 18CVRX. Use the collet that comes with the motor and you can use the flywheel from your original motor.

the 18CVRX is brutal! You would need to do a few other things to have it run strong and reliable. Biggest one is to change the gear ratio of the you clutch bell and spur gear. If you run your stock gears the 18 will top out way to fast and may even cause harm to your new mill by over revving. Plus it is darn right hard to drive when you pick up the front end constantly (wheelie at will). the new gears will help (also give higher top end speed), but, not solve the wheelie issue entirely. the next item is the clutch itself. the MIP 4in1 clutch just heats up tremendously, but, the aluminum clutch will not heat up as much and will lengthen the interval times between replacing bell bearings.

Oh shoot, cool, I found the link to the clutch.

http://www.ssrcracing.com/team-associated.html