73-87 Square Body Chevy & GMC C/K Truck Buyers Guide (Design, Options, Engines, Common Problems)

Square Body Truck Buyer's Guide! We'll cover the common problems, the specs, and everything else you've wanted to know about the 73-78 Chevy / GMC Trucks!
In terms of exterior design, the 3rd gen CK was a revolutionary design at the time. GM coined the term "rounded line exterior” for this pickup due to the rounded windshield corners, rounded corners of the cab roof, rounded-corner doors, slanted front fenders, and rounded pickup box corners. However, most owners and enthusiasts refer to these trucks are square bodies or box body.
The trucks were only available with a regular cab configuration, except for the crew-cab variant on the 20 and 30 series that offered four doors for 3 more passengers or more cargo inside the cab. The were 2 different styles of pickup beds available. The beds with fender flares were called Fleetside by Chevrolet and Wideside by GMC. They were available in 6.5ft and 8 ft lengths and depending on the year, both wood and steel beds were available. The Stepside by Chevrolet and Fenderside by GMC, was a narrow width flare fender pickup box featuring steps along with standalone tail lamps. Initially, only wood floors were available, but later models received steel floors.
Some other nice exterior elements include the wide front grilles, full doors that extended to the roofline, and the wonderful collection of different paint colors and finishes available. By now, you should have noticed all of the amazing color combinations and paint styles that these trucks were originally finished in. No truck today comes close to giving you all of the nice paint jobs that were available on the 3rd gen C/K pickups.
The interior in this generation of C/K reflected GMs past progressive attitude towards pickups. They knew that more and more owners were using their trucks as daily drivers, so they intended to make the trucks easier to use and more comfortable to live with.
This progressive attitude led to GM fitting this generation with some wonderful comfort features that weren’t usually available in pickups during the 3rd gen C/K production time frame. These included soft-touch materials were used throughout including the dashboard, (armrests), steering wheel, and shift levers. High quality grained interior panels and bright metalwork was used on the inside. Custom Vinyl which was a variant of vinyl or soft Custom Cloth and velour seating surfaces were used. Additionally, there was fabric headliners, door inserts, and deep plush carpeting, depending on the trim level. Higher trim levels used sound-deadening materials for quieter ride comfort. The wraparound dashboard had a full complement of gauges. There was an optional all-weather HVAC system with Air-conditioning that had the vents integrated into the dashboard, and owners could option an AM or an AM/FM radio with the radio antenna integrated into the windshield for a sleek look.
The GMC was available in Sierra, Sierra Grande, Sierra Classic, and the top-of-the-line high Sierra trim. The Chevrolet was available in custom deluxe, Scottsdale, Cheyenne, and its’s top-of-the-line-model, the Silverado. The high trim levels were plusher and had an emphasis on comfort and luxury.
In terms of engines, the third generation CK offered six-cylinder and eight-cylinder power plants as well as some Diesel engines. The entry-level six-cylinder was a 250 followed by a 292 six-cylinder. The 8 cylinder gas engines were available in 305, 350, 400, and 454 cubic inch displacements. The two diesels were 350 cubic inch and a 379 turbo diesel.
Looking at the data, you can see that the horsepower and torque figures are pretty low when compared to today’s engines. This is due to the fact that there was an oil crisis and as well as a strong push to get lower emissions by any means possible. These factors contributed to to create an era of low powered vehicles across most manufacturers.
The 4wd K-Series pickups were available with 3 different systems: a Conventional, a Permanent, or a Shift-on-the-move four-wheel-drive that was introduced for 1981. All K-Series pickups featured four-corner Vari-Rate multi-leaf springs, front live axle with symmetrical (inline) shock absorber geometry, and the Load Control rear suspension system. The 4wd pickups featured a transfer case that was bolted directly to the transmission and driveline components were installed as high as possible to reduce the chances of the undercarriage hitting obstacles, and to achieve optimal ground clearance. Steel wrapped Brake lines and an underbody skid plate optional.
There were lots of great options available on the C/K Pickup trucks. They included niceties like blow eye-line mirrors, power windows and locks, a tilt steering wheel, AM/FM stereo with cassette player, sliding rear window, fuel tank shield, rallye or styled wheels, A CB radio, cruise control, and deluxe or special two-tone paint finishes.
Watch this video to get the full scoop on the 73-87 GM Trucks!