Interpret Voltage Regulator Test?
 

The lights on my '78 SC grow brighter when the RPMs go up. The Optima battery charges and tests okay, so I performed a voltage regulator test as per the Bentley's manual. The manual states, "A reading much higher than 14.2 volts most likely indicates a faulty voltage regulator." "Much" is a rather ambiguous word.
My test on the original external regulator was 14.3. Is this "much higher"?
Is a new regulator recommended?

No, I don't believe that is bad. a 1/10 volt difference could just be the error in your meter. They are talking about hitting 15-16 volts is bad.

When the car is off, it shouldn't be more than 13V.

Having just changed my alternator, 14.5V is actually within range of expected at low throttle (2-3K RPM).

Prior to this, my VR was out and at 2K RPM, the multimeter read 16-17V.

Wow, 16-17v is up there!
So, the voltage regulator checks out, the battery checks out, now to find out what makes the lights brighter at higher RPMs.

Or maybe you should ask what is making your lights dimmer at low RPMs. Perhaps low RPM voltage output is low from the alternator. Maybe your high RPM light level is where it should normally be.