Welcome to the Forum James.
That generator head that you mention from Harbor Freight is designed to run at a steady 3600 RPM and the output is 120 or 240 AC volts. The output voltage is proportional to the RPM at the input.
You can use wind or water power to turn it. Wind power is not going to provide a steady RPM. You can gear it up so it can run close to 3600 RPM with full wind. However, you will need to take the fluctuating AC output and rectify it to DC, store it in batteries and then feed that to an inverter that will convert it back to a steady 120 or 240 AC volts.
If you have enough water flow (about 15 HP), you can gear it up to run at 3600 RPM and can use it as is, without the need to rectify it to DC.
I think the first thing you need to do is to determine how much usable waterpower you have.
There are other generators out there that run at lower RPM, I think they are better choices.
You are very fortunate to have good sources of water and wind power, take your time learning about it so you can use that almost free power.
Ed