Finally - I want to re-iterate to you the importance of getting that motor fixed -first-; like I said, look into local vintage automobile clubs in your area, you might find a person who was a mechanic of the era (heh - maybe you'll find a "Gus Wilson" old-timer who knows exactly what to do!) who can help you out, and get it working right. You might also find somebody who can help you install or set up a motor controller with PWM or a resistor pack, and do it in such a way so-as not to ruin the value of the vehicle (especially if it is a show car).
I agree with this approach and I remember the Gus Wilson stories as well. Keep in mind that the resistor(s) are generally in the shunt field circuit and the motor speed increases when the resistance increases. This is not a mistake, you really have to decrease the shunt field current (by increasing the resistance) to increase the speed.
Don