Wow!
Kinda gritty but interesting nonetheless.
Can I suggest that it may have better uses than wind?
The same conversion but in a hydro installation would deliver that 10kW continuously, like 7,200 kWhr per month. That's how much electricity I use in a year.
300 kg = 660 pounds. For wind, this will require a completely different kind of tower, as you say. I wouldn't want to make too many guesses about the tower until the performance of the WT is known. Unfortunately that piles one guess on top of another guess. Prepare for expensive footing and column, even doing it yourself.
I think Adriaan is on to something about split poles, too. The conversions I've done always run in parallel-star, because I make sure to disconnect the star point and separate the groups in each pole. Whenever I get around to upgrading my 24V system to 48V, then I'll reconnect the groups in series. A 6-pole motor may have an uneven number of coil groups per pole, so you can't divide three in half. Maybe you can split them 3 ways, so instead of 2 groups in parallel, you can have 3 groups in parallel. That lowers the volts per RPM- maybe too much. If so, then leave the groups in series, and maybe you'll enjoy very low RPM at the rated speed. The only way I know to be sure is to do the conversion and then bench test it.
Assuming you will craft the blades yourself, then you can choose the diameter, chord, taper, twist, and incidence according to the power output and speed profile of the converted generator.
I've typed this out because the image is really hard to read-
TEFC
Westinghouse T30/25/2006TE4
Poles 6
Frame 326T
60 Hz
Ambient 40C
volts 460
HP 30 / 25 / 20
Amps 30 / 31.0 / 25.0
RPM 1120 / 1120 / 1110
Weight 300 kg
PF 88.5%
Service Factor 1.1
Bearing 6312 6212
Ser. No. JS70791081005