Produced from 1973 to 1987, Square Body trucks are the third generation of the Chevrolet and GMC C/K pickups. The Square Body moniker comes from their box-like shape, despite being named the “Rounded-Line” generation by Chevy. The trucks feature a rounded windshield, door frames, and windows that contrast the box-body design.
The Square Body trucks were one of Chevy’s longest-running generations. With a 14-year production span, they aren’t as rare as other C10 generations, but they are easier to find. Their accessibility and affordability have made them popular choices for restorations and restomods.
Several notable changes occurred throughout the third generation of C/K trucks. Below is a list of those changes broken down by year.
The Square Body trucks brought drastic visual changes compared to the previous generation. A wider and larger frame gave the trucks a box-like appearance, leading to the Square Body nickname.
The trucks had a square wheel opening with round corners instead of the circular wheel wells. A rounded windshield and door frames balanced the boxiness of the design, while sculpted sides added dimension. With 20% more glass area, there were fewer blind spots for better visibility.
Chevy added a front stabilizer bar and reduced front spring rates. They also staggered the rear shock absorbers to help prevent wheel hop. Wheelbase for both the 6.5-foot box and 8-foot bed increased. The short wheelbase increased 2.5 inches to 117.5 inches, and the long wheelbase increased 4.5 inches to 131.5 inches.
The recessed egg-crate grille was only available for the 1973-1974 model years. Rain gutters above the door became available in 1974. Early generation models from 1973-1980 featured a different hood style than later models.
Chevy dropped the 307 V8 engine in 1973 and replaced the 402 with the more powerful 454. When the NP203 transfer case became available for models with the V8 engine, it had full-time four-wheel drive.
In 1973, Chevy also began offering the C30 one-ton dually with a crew cab. The C30 was one of the first modern heavy-duty pickups.
Available trim levels included the Cheyenne, Cheyenne Super, Custom, and Custom Deluxe.
The 1975 Chevy trucks were a hot product, with almost 750,000 vehicles sold that year.
Starting in 1975, Chevy revised the trim levels. They began offering the luxury Silverado trim that eventually replaced the C/K line in 1999. The Silverado took over from the Cheyenne Super as the top trim level. The Custom Deluxe became the base model as the Custom level was dropped. The Scottsdale edition was added as a new trim.
Along with the trim offerings, there were a few other changes between 1975-1976. The windshield wiper switch moved to a different location, no longer featuring backlighting. Rain gutters became standard on all models. The Fleetside models also received a quick-release tailgate.
The major difference when it comes to appearance is the grille change. From 1975-1976, the grille sat flush with the front and featured three horizontal bars. The engine size badge on the grille was removed beginning in 1976.
Catalytic converters became standard in 1975 for all trucks with a gross vehicle weight rating under 6,001 pounds.
The Silverado, Cheyenne, Custom Deluxe, and Scottsdale trims were available trims from 1977-1979. Another new grille design entered the scene for these model years. It's easy to differentiate these grilles from the rest as they have fewer vertical dividers and one less horizontal divider.
More hood details were also added in 1979, along with power windows. Early 1977 pickups featured low-back bucket seats, while later models had high-back bucket seats. An inside hood release was an optional feature.
The C10 was the only 1978 Chevy truck to receive a 5.7L V8 diesel engine. A new fuel filler door replaced the flush-mounted gas cap. There were over 1,300,000 trucks sold in 1978, which was a record-breaking figure.
Starting in 1979, the headlight bezels incorporated the front turn signals. The previous grille designs had separate headlight and turn signal housings. The same year, catalytic converters became standard on all trucks with a GVWR up to 8,500 pounds.
The 1980 Square Body Chevy is the outlier of the group. It features a unique egg-crate grille that was only made for one year.
Other than that, the body style pretty much stayed the same except for more chrome across the bottom of the grille. Rectangular headlamps became available and were standard for the Silverado and Sport trims.
A mid-generation refresh took place in 1981. Chevy introduced a new front end with redesigned sheet metal. Along with the changes came a 300-pound weight reduction. The same front sheet metal was used throughout the rest of the third generation until 1987.
Chevy redesigned the fenders as well as the hood hinges and vent windows. A new sloped hood replaced the previous hood design that had less rake. The windshield wipers moved from behind the hood to the top of the cowl.
Other exterior changes included optional quadruple headlights, new bumpers, and an updated tailgate. The bumper featured less detailing than before. Side markers were now horizontal rather than vertical.
In 1982, a chrome grille and bumper became standard on all trucks. A 6.3L 379 diesel became available with a 4-speed overdrive manual transmission.
The inside of the trucks also received a refresh with a new instrument panel, seats, dash shape, and sill plates.
Trim levels consisted of the Custom Deluxe, Silverado, Scottsdale, and Cheyenne. This was the last year Chevy offered the Cheyenne trim level, discontinuing it in 1982.
For 1983 and 1984, the Square Body Chevy featured a two-level grille. There weren't many other changes during this time. The turn signals changed location from the bumper to behind the grille. Along with the grille change, there were a few updates to the trim on both the interior and exterior.
Yet another redesign of the grille took place in 1985 and lasted until the end of the third generation. During this time, the 4.3L Vortec V6 engine with fuel injection became the most powerful base engine for Chevy trucks.
Beginning in 1987, the C/K trucks underwent a new naming designation. Model names switched from 10, 20, and 30 to 1500, 2500, and 3500, respectively. The Square Body C10 came to an end along with the C10 generation as a whole. The C1500 went on to become the Silverado, which remains Chevrolet’s most popular truck to this day.
Square Body ID Guide Infographic
For a quick reference, we put together this infographic to illustrate yearly changes during the Square Body generation. You can use it to help narrow down which used Square Body Chevy you’d like to buy.
[click the infographic below]
Sources: 73-87.com, Auto Restorer Magazine, trucktrend.com, fourwheeler.com, Truckin’ Magazine | Image Credit: Creative Commons, Creative Commons