Clutch Pedal Return Springs

The main thing you need the return spring to do, is pull the clutch pedal against the stop, and hold the fork and throwout bearing away from the pressure plate fingers.

Any spring that does that consistently will work.

When using one spring, pull from the fork toward the front of the vehicle. And make sure, the pedal is against the stop and the spring is stretched. The spring will stretch more when the pedal is stretched. 

The reason you want the spring stretched with the pedal up, is so it won't jump off when the pedal slams the pedal stop.