I'd like to help but I don't understand the question.
When you put an AC 1 voltage signal it applies 1V input across the whole frequency range. So the harmonics are already in there, it just does not distinguish between them and the signals that are not harmonics of what you consider to be fundamental.
For example, say your fundamental is 1 kHz, and you have an amplifier as DUT, and assume this is an AC analysis from 1 Hz to 1 MHz. When you apply AC 1 V at the input, it would just put 1 V from 1 Hz to 1 MHz, for the entire swept spectrum. And then you would see at the output which bands are being attenuated and which bands are being amplified without distinguishing between harmonics of the frequency you consider as fundamental.
So what you are saying is basically running an AC sweep and looking at the output only at specific harmonic frequencies, which is just a regular AC analysis, there's nothing special about it. Also keep in mind that AC analysis is a linearized analysis, so 1 kHz AC signal will not create harmonics at the AC output.
So I think you're confusing AC analysis with actual transient signal that has AC (alternating, periodic) behavior. Because that's not AC analysis is.
One other thing you might mean would be PAC (periodic AC analysis) which accepts a periodic steady state and runs the AC analysis over that periodic operating point. In this case it makes sense to say that you want to run the AC analysis over the harmonics because in this case you actually need to consider harmonics of the operating point.
So if you can be more precise on your question, that'd be helpful.