Try making the car with 2 by 6 plates for a wider car.
Note that if you use 1 by 6 or 1 by 4 plates there is not enough stability
to keep the car retangular shaped and so there is too much friction on the axles.

One motor can be used to generate electircity for a car motor.  Or even for two.

Connect one motor to another.  Moving one car moves the other.
Turn the way one lead (wire) is connected.  See which way they go.