Engine crossmember upgrade
These cars are supposed to have a piece of bracing, called an Engine Crossmember, that tie the bottom of the front frame rails together and help hold the front of car a little more square. More specifically, they help spread the side loading and prevent deflection of the suspension when the car is going around a turn.
My car didn't have one when I got it. I had to discover it in a catalog and ask myself "where's my crossmember?" Apparently, it's not terribly uncommon for these pieces to have been removed over the years to facilitate an oil pan gasket change or an engine pull or some other maintenance activity, and simply not put it back. It just became one of those 'extra' pieces.
Hint: if it's supposed to be on your car, it's not 'extra'. Ford was trying to pinch pennies until they bled as they made these cars. There wasn't a lot of margin in these cars. So try not to end up with a box of 'extra' parts when you do a project. It's bad form, and the next owner will not appreciate it either.