Expanding Seating Capacity in the Chevy C-60

[MikePhua]

The Legacy of the Chevy C-60
The Chevrolet C-60 was part of GM’s medium-duty truck lineup, produced primarily from the 1960s through the late 1980s. Built for durability and heavy hauling, the C-60 was a staple in agricultural, municipal, and industrial fleets across North America. With a gross vehicle weight rating (GVWR) ranging from 19,000 to 22,000 lbs, it was often configured as a flatbed, dump truck, or grain hauler. Its cab design was shared with the lighter-duty C/K pickup series, making it a versatile platform for customization.
General Motors, founded in 1908, dominated the truck market for decades. By the mid-1980s, GM’s medium-duty trucks like the C-60 were selling tens of thousands of units annually. Though eventually replaced by the Kodiak and TopKick series, the C-60 remains popular among restorers and custom builders due to its robust frame and classic styling.
The Seating Challenge in Medium-Duty Trucks
One of the limitations of the original C-60 configuration is its standard two- or three-person cab. For personal use or family-oriented builds, this poses a challenge. Unlike modern crew cab pickups, mid-1980s medium-duty trucks rarely came with extended or crew cab options. This makes expanding seating capacity a creative endeavor requiring structural modifications.
Terminology clarification:

• Crew Cab: A truck cab with four full-size doors and seating for five or six passengers.
  
• Sleeper Cab: Originally designed for long-haul trucks, this is an enclosed space behind the driver’s seat used for resting, often repurposed for seating in custom builds.
  
• MDT (Medium-Duty Truck): Trucks with GVWR between 10,000 and 26,000 lbs, used for commercial and vocational purposes.
  

Creative Solutions for Seating Expansion
Several approaches have emerged for increasing seating in a C-60 without compromising safety or aesthetics:

• Crew Cab Conversion
  Since the C-60 shares its cab structure with the C-30 pickup, one option is to source a crew cab from a C/K series truck and weld it onto the C-60 frame. This requires fabrication of additional cab mounts and alignment of body lines but results in a factory-like finish.
  
• Suburban Body Swap
  Another method involves grafting the rear half of a Chevrolet Suburban onto the C-60 chassis. This provides four doors and ample seating, though it demands significant structural reinforcement and drivetrain adjustments.
  
• Sleeper Integration
  Installing a sleeper cab from a semi-truck behind the original cab is a popular custom solution. By adding windows and a bench seat, the sleeper becomes a functional passenger area. Common choices include 60-inch Kenworth or Mack R-model sleepers, which are narrow enough to match the cab width and built with durable aluminum shells.
  
• Custom Fabrication
  For builders with access to fabrication tools, constructing a bespoke rear cab extension using steel tubing and sheet metal allows full control over dimensions and design. This route is labor-intensive but offers the most flexibility.
  

Cost Considerations and Market Availability
Used sleeper cabs can be found for as little as $400, especially at auctions or salvage yards. However, DOT-approved sleepers for MDTs often cost several thousand dollars. Crew cab donor vehicles from the 1980s and 1990s are increasingly rare but still appear in regional auctions and classifieds.
In 2021, a builder in Illinois successfully converted a C-60 using a 1987 Suburban rear section, integrating factory seats and climate controls. The project cost under $3,000 in parts and resulted in a six-passenger truck with vintage styling and modern comfort.
Powertrain Compatibility and Engine Swaps
When modifying the cab, it's important to consider engine performance. The C-60 was available with several engines, including:

• Chevrolet 366 and 427 big-block V8s
  
• Detroit Diesel 8.2L “Fuel Pincher”
  
• Detroit Diesel 6V53 and 8V53 two-stroke engines
  

For lighter payloads and minimal towing, a 4-53 Detroit Diesel may suffice, though it offers limited torque compared to the 8V53. Swapping engines is common in custom builds, with many opting for Cummins 6BT or Duramax diesels for improved fuel economy and reliability.
Terminology clarification:

• GVWR (Gross Vehicle Weight Rating): The maximum allowable weight of the vehicle including passengers, cargo, and fuel.
  
• Super Singles: Wide single tires used in place of dual rear wheels, often for aesthetic or off-road performance.
  

Safety and Legal Compliance
Any seating modification must comply with local vehicle safety standards. Key considerations include:

• Seatbelt installation for all passengers
  
• Structural integrity of modified cab sections
  
• Proper lighting and ventilation in added compartments
  

In some jurisdictions, reclassification of the vehicle may be required if seating capacity exceeds original specifications. Builders should consult with local DMV or transport authorities before finalizing modifications.
Conclusion
Expanding seating capacity in a Chevy C-60 is a rewarding challenge that blends engineering, creativity, and nostalgia. Whether through a crew cab swap, sleeper integration, or full custom fabrication, the possibilities are vast. With careful planning and attention to safety, the C-60 can be transformed into a unique family hauler or showpiece that honors its industrial heritage while embracing modern utility. As interest in vintage trucks continues to grow, such builds not only preserve history but also redefine what a medium-duty truck can be.