... You're new to forums aren't you?
The best pinion/ spur gears are up to you. Depending on how much torque and top speed you want. Knowing you so far, it sounds like you're going to want major top speed with torque. So your best bet is to gear it up as high as possible. I am not familiar with the pan car you have, but I know the Co-27 Pro stock (Make sure you get the PRO version. This is dyno tested and all that jazz) and it is an AWESOME stock motor. I have one myself.
People are going to ask you what you what kind of racing you do, and where you race. Though, judging by the way you asked it, you'll be driving like me in driveways and parking lots, so you can gear it up.
When I say gear up, I mean use a high pinion gear (on motor) and low spur gear (to the drivetrain). This will create a great amount of speed, and the torque from the motor is pretty good.
If you read anything from this post, read this: Experimentation is the only way to find out the best setup.
Sure you can ask everyone on this forum for their competitive racing setups, but it probably doesn't fit your style of racing.
Notice what happens to your car with different setups. WRITE IT DOWN.
See what works, and what doesn't. You are going to need patience to do this hobby... and all the experts you'll see are that way because of their patience, and experience.
Who knows, maybe you'll be the next Steve Weiss...
If you have any more questions about things, (which I am sure you do. Everyone always has questions
) just post em here. I know few people post in these kind of topics, but I'll surely check on it when I see it. Though, I have a TT-01 and am not familiar with your chassis.