Ford might not carry a group 27F battery anymore. I went to a local dealer to buy one a few weeks ago and was told that it was no longer available. The replacement was a Group 24 battery. Sure, that'll work, but it's smaller. It won't fill out the battery tray and the heat shield won't fit properly, either.
NAPA still carries Group 27F batteries. Advance Auto Parts does, too, under the Die Hard brand. I bought the Die Hard battery and it looks EXACTLY like the Motorcraft 27F except for the labels.