Board Thread:Game Help/@comment-26038919-20150126012224/@comment-7697305-20150126031542

I am fairly sure the change which made Meteor Heads unable to be farmed for key molds (and Souls of Light/Night, etc.) was only a change to that specific mob's drop table rather than to drop results for certain items.

So, any other farming methods for key molds (including methods which do not include mobs being killed by the player) should still work.