I believe the "hunting" you are seeing might be more "variations" as each cylinder does not receive the EXACT same amount of fuel/air mixture and/or spark energy. If each cylinder had its own intake tract of the exact same length, shape, and contours . . . combined with spark plug wires of the exact same length . . . AND with points, cam lobes on the distributor "cam" to open and close the points exactly the same for EACH cylinder, then you'd probably see less rpm variation at idle speeds.
Also, too, on some engines with a lot of metal "slinging around", as a Ford FE, these variations might of less magnitude as it would take a little more energy to make those variations happen, I suspect.
CBODY67
