Welcome to the forum
I assume you are talking about the key cylinders, they come in Chrome or Black.
You will need a set that fits 1989-1992 Ranger.
Put window all the way up
Remove door panel
You can see/feel a metal rod attached to the back of the lock cylinder, pull it off, might be a clip holding it, save it
In the door jamb where cylinder would be on the other side of the metal panel you will see a metal clip, slide it out toward you, that will release the cylinder and you can pull it out from the outside of the door.
On some there is a metal ring on the cylinder holding it against the door, you need to use a smaller screw driver to wiggle it back enough to remove it.
There is a Left(driver) and Right(Pass.) Door for these, so mark them.
A locksmith can sometimes rekey them.
You can also buy a Lock set that includes a new ignition key cylinder so doors and ignition use the same keys, or a locksmith can rekey ignition cylinder to match door keys.
Ignition key cylinder is very easy to swap out, just push a button under steering column
Found these on ebay: http://www.ebay.com/itm/NEW-PAIR-FOR...Model%3ARanger
You would have to determine if they would be the right ones