The Mustang underwent a complete redesign for 1971 and grew bigger in every way except performance. To understand what happened, it’s best to compare the big slab-sided car with the original 1965 model. The 1971 Ford Mustang was 7.1 inches longer than the 1965 model, 6.8 inches wider and around 500 pounds heavier. It was also 2 inches longer than the 1970 model, and 3 inches wider. Mostly it seemed bulkier, and hardtops had a high trunk with flying buttresses and a tunnel back window.

Sales dropped again, to 149,678 units divided into 65,696 hardtop coupes, 29,956 fastbacks, 6,121 convertibles, 17,406 Grand hardtops and 36,449 Mach 1 fastbacks. Prices began at $2,911 for the hardtop, $2,973 for the fastback, $3,227 for the convertible, $3,117 for the Grande and $3,268 for the Mustang Mach 1. The Boss 302 was gone, though a watered-down Mustang Boss 351 was offered, and the Boss 429 had vanished. A 429 engine option was offered, though it was based on the Lincoln 460 cid V-8.

A total of 10 engines were offered, with a base 155 bhp 250 cid six, a 210 bhp 302 cid V-8 in the Mach 1 and 330 bhp 351 cid V-8 in the Boss 351. Optional engines included a 210 bhp 302 V-8; a 240 bhp, 351 V-8; a 285 bhp 351 V-8; 370 bhp 429 and a 375 bhp Ram Air 429. All 351s were the Cleveland V-8.

The 428 CJ (Cobra Jet) was replaced by the 429 CJ, and no parts were interchangeable. The 429 was bigger than the 428 and one reason why the Mustang was redesigned. It was a large Boss 302 and an effort to make the 460 breath better, with bigger valves, four-bolt mains, forged rods and an 11.3:1 compression ratio. The CJ became the SCJ if the Drag Pack was bought, with 3.91:1, 4.30:1 or 4.11:1 rear end. A stiff competition suspension package was offered, and a dual Ram Induction option for 351 cid or larger engines.

Power windows and a rear defroster were offered for the first time, but the rear window slats were deleted as the fastback window was too flat. The dash was simplified to three large gauges, but enthusiasts could still get a sports option with gauges instead of warning lights and a tachometer.

The Mach 1 package was promoted, with the departure of the Boss 302, but sales still dropped. It used a different grille, with a urethane-covered bumper in body color, two driving lights in the grille and non-functional air vents. The hood and the lower body were black or silver, depending on the body color. Interior decor featured wood applique, molded door panels and knitted vinyl high-back buckets. Stripes and Mach 1 decals were applied to the exterior side panels.

The Boss 351 was a complete package with limited options. The 330 bhp Cleveland V-8 featured four-bolt mains, big valves, solid lifters, 11.7:1 compression, functional Ram Air intakes, a four-speed Hurst manual gearbox, 3.91:1 posi rear axle, power front disc brakes and spoiler and a chrome front bumper. The hood was mostly black and had two lock-downs.

The luxury model Grande got a full vinyl roof, lots of comfort and convenience accessories inside and cloth seats and exterior brightwork. It was available with all optional engines.

Nineteen colors were offered, though some of the best 1970 colors were gone. Here are the codes: Raven Black (A); Maroon Metallic (B) Dark Ivy Green Metallic (C), Grabber Yellow (D), Medium Yellow Gold (E); Grabber Lime (I); Grabber Blue (J); Wimbledon White (M); Pastel Blue (N); Medium Green Metallic (P); Light Pewter Metallic (V); Grabber Green Metallic (Z); Bright Red (3); Medium Brown Metallic (5); Silver Blue Metallic (6); Light Gold (8) Gold Metallic and Gold Glamour were special order. There were 29 interior combinations, and convertible tops were black or white.