Simply do some maths mate 56:1 worm drive gearbox, say 4:1 V-belt reduction drive to the pv frame. As you should know a DC motor's speed is controlled by voltage so depending on the condition required the voltage can be selected.
ie: 1. finding the right equal position for both led's to output the same voltage say 6-12 volts
2. Go to sunrise position at dusk pump 24 volts in for quicker travel.
By using an industrial wormdrive gearbox and further reduction with the V-belts will ensure enough rigidity to withstand huge gales.
Now for the led's do a simple test wire 2 led's up in parrallel with the output going to a gate on a fet which is connected to another led to show the circuit works. Now powerup a third led to shine directly into the 2 led array and watch the fet turn on. Simple isolated supply and a good test proving that led's DO output a voltage when exposed to light.
Hope that helps
cheers Bryan