Locks have been around for as long as 4,000 years according to reliable sources. Experts say they date back to the free-spirited Egyptians. The Romans got on board later with some of the first metal locks with springs, tumblers, and keys, similar to what we have today. Although most cars today have keyless entry, they still have the key-activated lock pioneered by the Romans. Chances are pretty good you use key locks several times per day depending on your profession and where you live. If you have charge of a variety of facilities or vehicles, keys fill your pockets with access to just about everything encountered in a given day.
Vintage Mustang locks aren't much different from those archaic mechanisms the Romans invented ages ago. They have springs and tumblers inside and are designed to work with only one particular kind of key cut specifically for that combination of tumblers. Over time and use, locks deteriorate to the point of requiring replacement.
There are other reasons for replacing locks, though. Ryan Peart of JGM Motorsports came to us with his lock problem. Seems he lost the door and ignition keys to his '66 Mustang. That's when we contacted Mustangs Unlimited, which sent us every type of lock imaginable for a '65-'66 Mustang-including glove compartment.

Mustangs Unlimited has the...

Mustangs Unlimited has the goods for your classic Mustang lock replacement, including new keys and attachment parts. Pony-embossed door and trunk keys are available at additional charge.

This is an illustration of...

This is an illustration of a typical '65-'73 door lock mechanism. They're all virtually the same across nine years of production. If you own a '74-'78 Mustang II, expect the same thing. It may surprise you to know that the '79-'04 Mustang locks aren't much different unless you have power door locks.

To access door locks, you...

To access door locks, you must first remove the door handles, armrest, and panels.

Once the rod-retaining clip...

Once the rod-retaining clip is disconnected, this spring steel retainer is removed to free the door lock.

This is what you can expect...

This is what you can expect to see inside the door. Shown here are two mechanisms. On top is the door release rod. Below is the door lock mechanism attached to the door with a spring steel clip, which is easy to remove. The rod is retained with a plastic/steel combo clip. Expect to use a plastic retainer unless you don't mind the expense of the steel clip shown. Steel clips were running upwards of $35 each at press time.

With the spring steel retainer...

With the spring steel retainer removed, the door lock comes out like this.