The 1973-1987 era, known as the “Rounded Line” or “Square Body” generation, featured a new, more modern design. Chevrolet and GMC trucks were tested in a wind tunnel and designed for better aerodynamics. This included rounded corners in key areas of the design, such as the windshield and side windows. The wheelbase was extended and a dual rear wheel option was offered on one-ton pickups. However, many enthusiasts refer to this generation as the “Square Body” Chevy truck due to its angular lines and squared-off wheel openings.
• 1973:
* An all-new carbon steel ladder frame with a “drop center” design was introduced.
* The fuel tank was relocated outboard of the frame rails, beneath the cab floor, increasing fuel capacity up to 40 gallons.
* Two-wheel drive trucks now featured independent front suspension, improving ride quality.
* A new grille design featured a larger grillwork and clear parking light lenses. The front fenders received new combination model nameplates and series identification plaques. The tailgate was restyled with a quick-release control.
* The 1-ton crew cab pickup was introduced, offering increased passenger capacity.
* The Crew Cab option was available, providing either 3+3 seating or lockable storage in the rear cab.
* Full-time 4WD became an available option on all V8 engine models.
* A new braking system was introduced that emitted an audible signal when the brake pads needed replacement.
• 1977: Power windows and power door locks were offered as optional features for the first time. A rear window defroster was also introduced as an available option.
• 1978: Diesel engines were introduced as a new powertrain option.
• 1979: A catalytic converter was added to trucks with a gross vehicle weight (GVW) of up to 8,500 pounds to comply with emissions regulations.
• 1980: The seat back angle was adjusted to enhance passenger comfort. A new thermostatic-controlled cooling fan was implemented. The 292 six-cylinder engine received a new single inlet dual exhaust system.
• 1984: Interior door panels were now made with two galvanized steel pieces for improved rust protection.
• 1985: A new custom two-tone paint treatment was introduced, applying the secondary color above the beltline on the Fleetside bed, the rear of the cab, doors, and fender sides. The Vortec V-6 engine was introduced as a new powertrain option.
• 1987: Carburetors were replaced with fuel injection across all models, improving engine efficiency and performance. For the 1987 model year only, the C/K designation was changed to R/V to distinguish these trucks from the upcoming GMT400 generation of trucks.