The latest innovative spark plug socket: 

9/16 Hex for 5.4 Liter Ford Engine

This versital tool enables the user to remove a spark plug with just one tool. It grips the plug with the spring-clip, keeping the plug in place when you go to install it and in place when you remove it.  It is extended in length for easy reach.  It's one piece construction eliminates extension and socket movement.  It has a 3/8 square drive top and 5/8 outside hex drive for use with open end, box end or ratched box end wrenches.  It has a knurled finger-grip for easy and true sparkplug starting.  Helps elimate cross threading.

9/16 Hex for Ford: (P/N 300F) - $65 Each