It has been my experience that probably 90% of all 'clutch chatter' is caused by either a worn pilot bearing, --a worn input shaft, ..OR both.
Generally speaking, oil-saturated clutch discs that slip enough to generate heat and warp the pressure plates will cause the clutch pedal to vibrate (pulsate) upon slight pressure but when you think about it, if the pilot shaft & bearing along with the input shaft bearing are within specs, the clutch will spin parallel with the flywheel face, and the pressure plate no matter how warped will still engage the disc without chatter. Again, a slight pedal vibration may be felt but that is all.
Now HERE is something that we have found quite a bit of, ...many Model A's suffer from pilot bearings that are worn off-center. This is likely caused by incorrect flywheel housing alignment where the input shaft is actually cocked within the bearing.