I have an old Snap-On Tools wrench made for the can-type oil pressure sender I use, but not worth the trouble of tracking down for the occasional use. I've owned several 351C and 429-powered vehicles, so it has come in handy. Before I acquired the Snap-On tool, I usually had good luck using a 9/16" crow's foot socket wrench or a short standard wrench, as others have posted. I've run into several of those where someone has already messed the 9/16" hex and left the mess for someone else. Some have tried to remove the switch by using the can. Occasionally it will come loose, and then as happens to most people, the can will break loose and spin on the base. Considering the location on a 351C or 429, the hex can be hard to get a standard wrench on. You may end up doing as I did once to help a friend who really messed his sender up. By the time he had decided he wanted to share this fun with someone else, the can was already sheared, and the hex was rounded out. There was nothing left to do then but to keep tearing it apart until nothing was left but the base. Just be careful to check for any metal debris before removing the threaded part of the sender from the block.
Even though I tend to plug Motorcraft products a lot, You don't necessarily have to use a Motorcraft sender. The Motorcraft gauge sender is Ford # E4ZZ-9278-A or Motorcraft SW-1547-B. If using a parts house such as Napa, Advance, etc., make sure you get something from their premium line.