Without reading all the pages of this thread, I would just like to chime in with the setup I had.
I used a 1978 Ford f150 alternator.
Was prolly a 60 amp unit.
Opened it up and removed the voltage regulator.
Re-routed the diodes outside the case and re assembled the case. I used a variac for the excite wire and a bridge rectifier to make the output 3-phase unregulated DC
It worked nice but I wish I would have been able to fluctuate the rpms of the motor. All I had was a one speed motor and so I never was able to change the frequency of the output. Hope this helps.