[Si Coe]

I'm not taking mine apart to count teeth, but I can say that it comes with 3 different sized pinions in the box, and these pretty much cover the whole gear range offered by the motor mount. IFIAK nobody sells different pinions or spurs.
Switching to brushless means removal of all the stock electrics. The stock receiver and servo are a combined unit, so switch to a brushless esc means a new receiver too, which needs to be very small ie pricy. Also the servo uses a weird 4 wire plug that only works with the stock receiver so you'll need a new servo too. And it has to be a JR SM22 as nothing else fits. Since the SM22 has a different spline pattern from the stock servo a specific servo saver for it is needed.
Basically brushless isn't worth it. The Atomic BB 2 provides plenty of speed and can calmly pull the largest pinion but works with the stock esc. If thats not enough, go Lipo not brushless. The Lipo pack is cheap, 7.4V instead of 4.8V so faster and also gives longer run times.