In reality 13.8 to 14.2 is really what you should have. Factory ammeter? Have you checked voltage at the regulator? My book shows a dark blue and a dark green plugged into the regulator.
When the car is sitting there running at idle:
What is battery voltage?
What is the voltage at the dark blue wire at the regulator?
What is the voltage at the output of the alt.?
You should get the same voltage at the battery as you are seeing on the dark blue wire on the regulator, maybe .4 volts less at the regulator.
Was it a factory 100 amp. alternator? it might have been because of rear defroster and A/C.