MG GM alt. Purists hit delete! Drivers read on.

Hi,
Thanks to all who responded to the "Why is my little red light on?"
thread.  The GM alternator is on.  It cost about $50-60 and about 2
hours labor.  But, it puts out 14 volts and can put out 60 amps.   It
has a lifetime (who's lifetime?) warranty.  I plan to rig a circuit that
will turn the little red light on if the voltage drops below 13 while
it's running.  It should cost about $5, I think.  Or, has anyone BTDT
and have suggestions?
Cheers,
Derf