This is no different for a stepper motor than any other form of motor. Gearing is normally provided to increase torque at the expense of velocity.
Since we know that stepper motors are inherently slow then check the gearing ratio on your motor before buying!!
If you want it to drive the main wheels then finding out that the maximum rate you can send steps, plus the gering ratio, means that it takes 30 seconds to rotate your drive shaft through one revolution (even with incredibly high torque) may make the motor unfit-for-purpose.