As Snook mentioned, if you want lots of torque and less top speed - a greater number of teeth on your spur, and less teeth on your bell clutch/pinion.
Go into your hobby shop and ask for their biggest spur and smallest bell clutch.
Or another option that wont cost you anything is to use your trigger finger to moderate the speed.
It doesn't take much skill to floor it and run your car at full throttle. One of the hardest things to master is throttle control. Perhaps set up a short course with a few tight turns and practice throttle control and to use your brake.
If your vision is not 100%, even an oval or kidney shape track can be a challenge when you are learning - try and get faster around the track by using the right amount of throttle and braking at the right time - the fastest way around the track will not be on full throttle all the way around, and you may find you want to change your suspension, and eventially, you will want MORE POWER!