We recently purchased a used 1996 Geo Metro Sedan (in the forum parlance, a "4/5"). It was cheap, and mechanically sound (so far as we could determine), but it had a lot of minor problems: cosmetic, trim, and electrical.
One of the biggest problems was that the driver's door didn't open from the inside. It doesn't sound huge, but coupled with the frequent Florida rain, and the driver's window not seating properly when rolled up... well, it needed immediate fixing. I had thought the problem was just a slipped actuator rod, but it turned out that the latch mechanism was borked.
Locks online were $70 and up. Junkyards didn't have much in the way of Metros. I eventually found a '96 Metro Hatchback with a working lock; it looked the same to me. 30 minutes of swearing, 1/8 teaspoon of blood, and $20 later, I was ready to fulfill my wife's fondest wishes.
When I got the latch home, I found that the actuator rods from the outside handles were different. It only makes sense: the door is longer and wider on the two-door, so the handle goes in a different location. Worse yet, the actuator rods were held on by a rivet.
Time for a little shadetree mechanicry.
By examination, I could tell that the ends of the actuator rods were unused. I could cut them off... but that makes my wife nervous. Instead, I planned to split the ends, bend them, pull the rods off the rivets, and swap them. Then I could bend them back, restoring them to nearly-original condition.
Step one: cut a slot in the actuator rods. Look at the sparks fly!
Wasn't that fun? I'm pretty shaky holding the Dremel left-handed, but otherwise you wouldn't have seen such awesome sparks. Or you would've seen my clothes catching fire, as they would've all been spinning towards me. You'd probably enjoy that, but I have my own preferences, thank you very much.
Next, I bent half the rod up and the other half down, thus creating a gap through which I could slide the rivet. Just pull it... uh, slide it back, getting the top half above the rivet... er, slide back while slightly twisting your wrist... darn it.
You know, this seemed a lot easier in my head. I had to open it up a little bigger. Twice. Eventually it slipped off, just like you see in the picture.
Eventually the thing came off. The picture above shows how wide I had to make the end gap.
I repeated the process with the existing (4-door) lock mechanism and actuator rod. After sliding the desired actuator rod onto the working latch mechanism, I straightened out the bend. The slot is still there, of course, and it will be weaker than the original, but since it never gets used, that's no problem.
Installation is the reverse of removal. :) It turned out the latch was a little stiff, but some WD-40 fixed that. We now have a four-working-door car!