basic power generation question (and alternators)

Hi there,
I have been trying to get a question answered and am running into road
blocks, could you possibly help as the experts in the area? Be gentle
with me, i've forgotten a lot of this and consider myself a basic
rookie! Here's the scenario...

Imagine a 3 phase induction turbine, similar to what's used for wind
mills. Smaller ones (say a 4 - 10' diameter blade configuration) are
"geared" to operate at peak efficiency around 20 - 25 mphs about 10-12
m/s - (I think that's about 500 rpm up to about 1200 rpm). This is so
because that's what average wind speeds usually are and they are
designed to generate power at low wind speeds. What if you had a
consistent high wind speed? Is it possible to "gear" these smaller
turbines for peak efficiency at 50 or 65 mph instead? OR, Could one be
purchased separately (sort of "off the shelf") and then it's rotating
shaft be "fit" for small wind blades. Put simply, I need a 3 phase
alternator (or whatever is most efficient for generating and storing)
that runs at higher rpms efficiently
WITHOUT the 30 metre diameter blades and associated price tag. Also,
would a 12 volt or 48 volt alternator be a better choice. Any
suggestions at all or where I might further research would be great. I
thank you kindly for your consideration and any help you could provide
me. Thanks a million, Pete