I'm thinking about building one of these. I sent an email to the company, I'm sure you can figure out what I asked from the reply 
Most of the 1/8 competition motor You can find currently on the market will fit the SSX823. The usual length of the motor is 68-72, but the absolute maximum space available is 78,5mm
Minimum distance between the center of the axle to the motor center is 28,5mm. maximum is 35,4. For stock gear (64T 32DP) You can fit pinions between 8T to 25T (sure 8T is too small to be usable so You're looking for minimum 10T. The max diameter of the can is 44mm.
Could fit a nice big motor in here!
Most of the 1/8 competition motor You can find currently on the market will fit the SSX823. The usual length of the motor is 68-72, but the absolute maximum space available is 78,5mm
Minimum distance between the center of the axle to the motor center is 28,5mm. maximum is 35,4. For stock gear (64T 32DP) You can fit pinions between 8T to 25T (sure 8T is too small to be usable so You're looking for minimum 10T. The max diameter of the can is 44mm.
Could fit a nice big motor in here!
