A lucky find right enough. If I am recall correctly, Northern Power use permanent magnets for their wind turbines. The generator is connected directly to the turbine, dispensing with the cost and losses of a gearbox. This means the rotor will rotate at about 20rpm or less. That in turn means that the internal arrangement must be more than 100 pole if it is to produce AC at 50 or 60 Hz directly. If the output is rectified and then applied to an inverter, then the number of poles doesn't matter. I played around with an old motorcycle alternator in this way back in the late 1980s, but I never took it very far.
If I understand correctly, the alternator you have was rated for use at 2000 rpm. From the rated output, you can work out the torque that the magnets produce. As a rough guide, If you reduce the rpm, the maximum power output is reduced in proportion. Iron and Copper losses are not linear, and how you rewind the stator will determine the actual power you will be able to produce.
Have fun with it whatever you do.
All the best. Jim. heronmeadows.com