ahhh, the ultimate Skygod spoke.
What happens on the Kingairs with no autofeather fitted? Glad you're not flying those!
Good point.
Even the FAA MMEL says "C" item... May be inoperative provided:
a) Aircraft is not modified with STC SA2307CE, and
b) Aircraft is not equipped with Four Bladed Propellers.
Back to you, Master of flying....