the ametek is a DC MOTOR that ,when spun at
1000 RPM produces about 38 volts at no load , and about 31 Amps at max load
750 RPM produces about 28.4 volts at no load ,and about 26 Amps at max load
500 RPM produces about 21 volts at no load ,and about 25 Amps at max load
Much like solar panel ratings you will not see NO LOAD voltages when charging batteries etc and AMPERAGE is measured with maximum loading,
The two readings do not occur at the same time but are necessary to plan regulation parameters but figure 60 to 75 % voltage and current when in use.(GUESS)
It should take a large blade to turn through gears or pulleys to get that kind of RPM while charging a battery bank..I don't do much with wind,except break it.
I would build a water wheel ,like an old fashioned mill,to develop the power to spin such a motor/generator at consistent speed.
It is a good find but parts to maintain the AMETEC are somewhat hard to find.
Data and opinion on this is based on internet research,not actual hands-on work with this motor.
I use Delco alternators or DC motors from water well pumps.Without guy wires and blade clearence height above your building ,the tower will not take the stress
and you would not like the noise factor of the blades will be quite noisy in use. A water wheel with split 55 gallon drums and good water flow might prove quieter and effective.
Good luck with the project.