Did you read the sticky thread I linked above?
The FH20 is just newer version of the FH012 per the theme of that thread
Yes, that is a good upgrade
However you need to be certain that the Stator is good.
Since you replaced the Regulator (even if with std type) that suggests something else is the problem
Originally Posted by 995 mike
I have tested stator windings. OK pairs of wires producing required AC volts when disconnected from rectifyer....
Just to say 'producing required volts' is not enough Mike:
You need to compare all three phases and they need to be equal (at any given rpm)
What are the actual
AC volts at idle
Did you do the isolation test between stator & ground?
Did it pass that?