You can definitely run a power rack without the controller. The issue will be tuning the torsion bar to the weight and handling characteristics of the particular car, and the fact that "road feel" will be deminished at higher speeds.

These are the two main benefits of the electronic controller. It allows fine tuning, and it gives good assist at slower speeds, yet you don't lose road feel at higher speeds because the assistance is turned down.

Think 70s type power steering as opposed to the current OEM type of power steering.