@CosoGuitars

This is an over-simplification of things I have recently learned about guitar pickups:

Impedance is what you'd expect
R + L (at +90 degrees) + C (at -90 degrees).

The resonant frequency of the pickup along can be approximated by:

1/ 2*pi * sqrt(L*C)

But this doesn't tell you the slope from resonat F to -12db (drop off freq) --think of pickup as a low pass filter.

(continued)

It also doesn't tell you anything about magnetic field strength. If the field is too low, weak signal. If it's too strong, it affects the strings creating an unpleasant harmonic distortion that is shrill.

Also, it doesn't tell you the effect of the guitar cord or the load (amp or DI box) which affect the resonant frequency.

(contd)

And probably more important, it tells you nothing about the speakers which have both electrical RLC properties and mechanical properties that affect the frequency spectrum and resonant frequency.

Yep, you can't tell how that pickup is going to behave until you employ it in the full circuit. You can make educated guesses, but even an crappy guitar cable can diminish your tone.

So how do people do this? It's not those R ratings you see that manufacturers put out.

Experience and some estimates are about all you have to work with.

It's an art more than a science, sadly.