The Squarebody (1973–1987) C/K series is one of the most popular and most-built generations of full-size Chevy trucks. This guide covers how to identify your year, trim, and configuration so you can order the right parts and build accurately.
Year Breakpoints & Key Changes
1973–1980 (First Series)
- All-new squared-off body style replacing the rounded “Action Line”
- 1973 only: rear leaf springs on C10 (K10 had them earlier)
- 1975: Catalytic converter added; smog pump on many models
- 1977: New grille design; optional new trim levels added
- 1980: Last year of the Oldsmobile diesel option on some trims
1981–1987 (Second Series)
- 1981: Major front clip update — new “aerodynamic” grille and headlight surround
- 1982: Diesel options expanded; new electronic throttle body injection (TBI) on some
- 1985: Fuel injection standard on gas engines (TBI 4.3L and 5.0L); carbureted engines still available
- 1987: Last year of the Squarebody (1988 = GMT400 redesign)
C vs K vs R vs V
| Code | Drivetrain |
|---|---|
| C | 2WD, conventional rear drive |
| K | 4WD, full-time or part-time |
| R | 2WD with revised suspension (later years) |
| V | 4WD variant of R |
For most Squarebody owners, it’s simply C (2WD) or K (4WD).
Cab Styles
- Regular Cab (C/K 10/20/30) — Two-door, bench seat
- Crew Cab — Four-door, larger footprint (rare in this era)
- Blazer — Two-door SUV on the C/K platform, removable top
- Suburban — Four-door SUV, no removable roof
Bed Styles
- Stepside — Separate rear fenders, narrow bed with running boards
- Fleetside — Flush bed sides matching cab width
Trim Levels (C/K 10/20/30)
| Code | Trim Name |
|---|---|
| None / Base | Standard / Custom |
| C | Cheyenne |
| S | Scottsdale |
| SB | Silverado |
Silverado was the top trim — chrome everywhere, full interior, and velour seating on later models.
Engine ID
| Engine | Displacement | Type |
|---|---|---|
| L25 | 250 ci inline-6 | Base |
| L22 | 292 ci inline-6 | HD/trucks |
| LS9 | 305 ci V8 | 4-barrel carb |
| L65 | 350 ci V8 | 4-barrel carb (most common) |
| L69 | 400 ci V8 | Big block light duty |
| LS4 | 454 ci V8 | HD/heavy duty |
Build Code / VIN Decoding
Pre-1981: Use the cowl tag (inside the engine bay, firewall) to find build options.
VIN format (1973–1980): 13-digit VIN on the dash and doorjamb
VIN format (1981+): 17-digit standardized VIN
Key VIN positions (1981+):
- Position 4: Series (C = 1/2-ton, K = 4x4, etc.)
- Position 5: Cab type
- Position 8: Engine code
- Position 10: Model year (B=1981, C=1982… H=1987)
Use these codes along with your cowl tag to build an accurate profile before ordering restoration parts.