Conception and styling

As Lee Iacocca's assistant general manager and chief engineer, Donald N. Frey was the head engineer for the Mustang project — supervising the development of the Mustang in a record 18 months from September 1962 to April 1964.— while Iacocca himself championed the project as Ford Division general manager.

Drawing on inspiration from the mid-engined Ford Mustang I concept vehicle, Lee Iacocca ordered the development of a new "small car"to vice-president of design at Ford, Eugene Bordinat.

Bordinat tasked Ford's three design studios (Ford, Lincoln-Mercury, and Advanced Design) to create proposals for the new vehicle.

The design teams had been given five goals for the design of the Mustang: It would seat four, have bucket seats and a floor-mounted shifter, weigh no more than 2,500 pounds (1,100 kg), be no more than 180 inches (5 m) in length, sell for less than US$2,500 (equivalent to $24,560 in 2023), and have multiple power, comfort, and luxury options.

Design, 

The Ford design studio ultimately produced the winning design in the intramural contest, under Project Design Chief Joe Oros and his team of L. David Ash, Gale Halderman, John Foster, and George Schumaker. This design was called the Cougar by the design team.

Oros states:

I then called a meeting with all the Ford studio designers. We talked about the sporty car for most of that afternoon, setting parameters for what it should look like — and what it should not look like — by making lists on a large pad, a technique I adapted from the management seminar. We taped the lists up all around the studio to keep ourselves on track. We also had photographs of all the previous sporty cars that had been done in the Corporate Advanced studio as a guide to themes or ideas that were tired or not acceptable to management. Within a week we had hammered out a new design. We cut templates and fitted them to the clay model that had been started. We cut right into it, adding or deleting clay to accommodate our new theme, so it wasn't like starting all over. But we knew Lincoln-Mercury would have two models. And Advanced would have five, some they had previously shown and modified, plus a couple extras. But we would only have one model because Ford studio had a production schedule for a good many facelifts and other projects. We couldn't afford the manpower, but we made up for lost time by working around the clock so our model would be ready for the management review.

In a 2004 interview, Oros recalls the planning behind the design:

I told the team that I wanted the car to appeal to women, but I wanted men to desire it, too. I wanted a Ferrari-like front end, the motif centered on the front — something heavy-looking like a Maseratti , but, please, not a trident — and I wanted air intakes on the side to cool the rear brakes. I said it should be as sporty as possible and look like it was related to European design.

David Ash

L. David Ash is often credited with the actual styling of the Mustang. Ash, in a 1985 interview speaking of the origin of the Mustang design, when asked the degree of his contribution, said:

I would say substantial. However, anyone that says they designed the car by themselves, is wrong. Iacocca didn't design it. He conceived it. He's called the father of it, and, in that respect, he was. I did not design it in total, nor did Oros. It was designed by a design group. You look at the photograph taken at the award banquet for the Industrial Designers' Society where the Mustang received the medal; it's got Damon Woods in it (the group that did the interior), and Charlie Phaneuf (who was with Damon), and it's got myself and John Foster (who was with me), it's got (John) Najjar in it.

So nobody actually did the car, as such. Iacocca in his book flat out comes and says I did the car. It's right there in print, "It's Dave Ash's Mustang." Bordinat will tell you I did the car. This book tells you I did the car, but, in actual fact, I had a lot of help, and I don't think anyone ever does a car by himself, not in these times anyway.

Gale Halderman

Gale Halderman, in a 2002 interview with Collectible Automobile, spoke of the Mustang's evolution through the Ford design studio:

Dave Ash had started a clay model of the car. He had this very boxy, very stiff-looking car. Joe came back from a management conference, saw it, and said, "No, no, no, we're not going to do that!" That's when he came to me… he said, "…we've just been given an assignment by [Gene] Bordinat to do a proposal on a small car that Lee [Iacocca] wants to build. We've got to do one, and I want you to work on that project." I went home and sketched some cars, and I took about five or six sketches with me the next morning and put them up on the board.

We must have put 25 sketches on the board that morning, because Joe assigned three or four of us to do designs. Joe picked one of the sketches I did at home to be clay modeled… so we actually started over on [Dave Ash's] clay model with the theme from one of my designs, which had scoops on the sides and the hop-up quarter lines.^[

To decrease developmental costs, the Mustang used chassis, suspension, and drivetrain components derived from the Ford Falcon and Fairlane. It used a unitized platform-type frame from the 1964 Falcon and welded box-section side rails, including welded crossmembers. Although hardtop Mustangs accounted for the highest sales, durability problems with the new frame led to the engineering of a convertible first, which ensured adequate stiffness. The overall length of the Mustang and Falcon was identical, although the Mustang's wheelbase was slightly shorter. With an overall width of 68.2 in (1,732 mm), it was 2.4 in (61 mm) narrower, yet the wheel track was nearly identical. Shipping weight, approximately 2,570 lb (1,166 kg) with the straight six-cylinder engine, was similar to the Falcon. A fully equipped V8 model weighed approximately 3,000 lb (1,361 kg). Although most of the mechanical parts were from the Falcon, the Mustang's body was completely different, including a shorter wheelbase, lower seating position, and lower overall height. An industry first, the "torque box" was an innovative structural system that stiffened the Mustang's construction and helped contribute to better handling.

Gale Haldeman spoke of the engineering and design of the car in his interview, stating:

No one knew the Mustang was going to be as popular as it was, but it created a huge stir in the company. Everybody just loved it, even the engineers, though we must have bent 75 in-house engineering and manufacturing rules. The Mustang had the first floating bumpers. The whole front end was a die-casting with a floating hood.

There were so many things the engineers said we shouldn't be doing, but they didn't want to change them either. There was so much enthusiasm right from the beginning. Even the drivers at the test track loved it. We would go there for meetings, and the crowds of people around it were huge. That was totally unusual, so we suspected the Mustang was going to be a hit.

The idea for a fastback originated with Joe Oros as well and was designed in Charlie Phaneuf's studio. Haldeman recalls:

We did it in secret. No one, including [Hal] Sperlich or Iacocca, saw it until it was finished. We cast it in fiberglass, painted it bright red, and then showed it to Iacocca. He said, "We've got to do it!"

An additional four-door model was designed by Dave Ash as a clay model, but was not considered.