if you are intent on an automotive alternator, you might look up a prestolite/leece neville 110-555jho, at least it has large ball brgs front and rear. it is a large frame truck alternator, and has a much larger diameter rotor and stator than the puny delco 10si which is a joke.

in stock form the 555 will produce about 90 amps into a 12volt battery at around 1500rpm, so i would expect maybe if rewound around 20 or 30 amps at maybe 400rpm.

but you still have the rotor current about a 100 watts worth that is a loss, unless you fit the rotor with neo's.

i would go with the 555 anyday before a delco for a windmachine, at least you would get something that might be useful for all the effort.

check your local hd truck dealers, the core alternators go in the scrap bin, no one will rebuild them because they sell the so cheap you can't afford to invest even an hour in labor to rebuild one. you should be able to get a core for free and they usually only need new brushes or maybe a regulator.

of all the automotive alternators the 555 is probably the one most able to get you something in return for your effort.

again the 10si is a joke in my opinion,