Here are your options:
* Locksmith: This is usually the most affordable and convenient option. A locksmith can either make a key based on the ignition cylinder (if you still have the lock cylinder), or possibly by decoding the lock from the car's VIN. This second option is less reliable and may not be possible. The locksmith will have the tools and knowledge to accurately cut the key.
* Dealership (Ford Dealership): While more expensive than a locksmith, a Ford dealership (Mercury was a Ford brand) might have access to your car's key code if it's still on file. They can then order a key or cut one for you, although they may need to see your vehicle registration for verification. Note that this is less likely after all these years.
* Alternative Key Makers: Some auto parts stores may have key-cutting services, but their ability to duplicate a 1991 Capri key may be limited. It's best to check with them beforehand.
What you will likely need to provide:
* Vehicle Identification Number (VIN): This is essential for a dealer to potentially look up key codes.
* Proof of Ownership: A dealership may require this.
Important Considerations:
* Ignition Cylinder Condition: If your ignition cylinder is worn or damaged, a new key might not work perfectly, or might even damage the cylinder further. The locksmith will likely be able to assess this.
* Cost: Expect to pay more at a dealership than at a locksmith.
In short, don't try to make a key yourself. Getting a professional to do it is the only reliable way to ensure your new key works correctly and doesn't damage your car.
