I was doing research on a 58 AC system and found the attached picture of the AC vents on a 56 ford along with your post asking questions about Ford AC. The 56 vents are around the radio speaker grill. The 57 Ford had the vents in the trim at the base of the windshield. In 58 the vent was moved to the bottom of the dash. Hope the picture helps. Here's the URL of the site where I found the picture.
http://collectiblecarcorner.blogspot.com/