Thanks to Dennis Weaver :

The ignition lock cylinder is the part that wears out and allows what I am going to call the bezel for lack of anything else to go around and to not line up when you have the key out of the ignition. The part is about $45 list and less if you have a Ford dealership that will work with you. You do not need the electronics which is what must have cost some so much and you do not need to re-key anything to get the doors to open with the ignition key.

The ignition cylinder comes in 5 configurations for each year of the Taurus: A, B, C, D, and E.  Each configuration correlates to the #6 (sixth) cut on the key, counting from the pointy end of the key.  (Igintion part A is for a #6 cut 1 unit in deep. Ignition part with E is for #6 cut that is 5 units in depth.--see below for explaination of the differences in depth and the number it corresponds to.) The #6 cut on the new ignition must match the #6 cut on the door key. So you take your ignition key to the dealer, he has a gauge that will measure the 10 cuts on the ignition key. (If he doesn't have this gauge--find another dealer!!) He will match up the appropriate ignition switch with your present key. The new ignition
cylinder comes with 2 keys with cuts 1, 2, 3, 4, and 6 already cut, these are the ignition switch cuts. The dealer then takes your original ignition key and duplicates cuts 5, 7, 8, 9, and 10 onto the new keys that came with the new ignition cylinder--these cuts open your doors.

Now let me explain that the depth of each cut is from 1 to 5, 5 being the deepest and the key is bilaterally symmetric, so it will work either way. Unlike GM or Chrysler, there is no up or down on the keys, but you know this. Now here is where Ford got a little confused. Your ignition key has a ten digit number, this number is the depth of each of the cuts read from the hilt of the key out, but the ignition replacement part number reads the depth of the cuts from the point in and requires cut #6 to match, so cut #6, as described in the lock replacement part directions, that must match the doors and ignition is actually the 4th digit in your key number. This lack of consistency gives dealerships trouble.  I talked to my parts guy and he said Ford dealerships all over the area send people to him to get there ignitions replaced because these other dealerships can't figure out why the ignition cylinders they install don't work most of the time.
Some dealerships have apparantly given up and must just find it easier and more profitable to screw the customer out of lock sets than to try to figure this out. He wasn't' surprised when I told him some of the horror stories from this list--$430 comes to mind, and sends shivers down my back. This is apparently such a common problem within dealerships and is such a common problem with our cars, it needs to become common knowledge among us on this list.

A locksmith had this to add :

Cuts 1-6 are the door cuts and 5-10 are in the ignition the common cuts are 5 and 6. A new ignition can be purchased through a locksmith for about $25.00 and be rekeyed for about $10.00. Most of the time I have been able to re-stake the ears or what you call the bezel for about $15.00. and you are right the dealer will  try to tell you need new locks or at least the ignition replaced. He won't tell you that the manufacturer of the ignition could solve the problem by simply inserting a roll pin in the lock to keep the ears from spinning. they are only crimped together. Do to wear and tear the crimp spreads apart leading to the problem in discussion. The ears spinning and the key not able to go in.  Also going to a locksmith to purchase or taking a lock allready purchased to a locksmith they can add the missing 5 wafer that the new lock does not have. this will give the same security the original ignition had. Not doubting your parts guy on other thing he knows but he to is mis-informed about this ignition.