355-Powered 1968 GMC C2500 Pickup 4x4 Conversion

Description

The 1968 GMC C2500 and K2500 were part of GMC’s second generation of C/K trucks, produced from 1967–1972 and known as the “Action Line.” Introduced during a pivotal era of truck modernization, these models combined rugged capability with increasingly refined styling. The ’68 lineup featured bold lines, a broad grille, and squared-off wheel arches.

The C2500 represented the two‑wheel‑drive 3/4‑ton platform, while the K2500 offered four‑wheel drive for heavier-duty use. While GMC trucks of this period shared chassis and sheet metal with Chevrolet models, GMC continued offering its own V6 engine options.

This 1968 GMC began its life as a 2WD C2500 with an inline-six, but the seller has transformed it into a V8-powered 4WD version closely resembling a K2500. The pickup’s many upgrades include a Chevrolet 350-cubic-inch V8 (bored .030” over to 355ci) with performance upgrades, a rebuilt Turbo‑Hydramatic 350 (TH350) three-speed automatic transmission; four-wheel drive with an NP205 transfer case, and a Classic Instruments electronic analog dashboard cluster. The fuel tank has been moved to the rear of the truck, and the factory frame and body were disassembled, sand-blasted, and primed. The truck remains finished in primer.

This upgraded ’68 GMC is now offered with numerous spare parts, some parts receipts, and a clean Ohio title in the seller’s name.

Highlights

• Long-term build since being purchased as a barn find in 2010

• Modified C2500 to four-wheel drive with NP205 transfer case

• Original inline-six engine swapped for Chevrolet 350ci V8 bored .030” over (355ci) with performance upgrades

• Original transmission swapped for GM Turbo‑Hydramatic 350 (TH350) three-speed

Factory Equipment

• Bench seat

• Sun visors

• Rear slider window

• The chassis number (CS20DZB13971) decodes as:

  • C – Conventional cab (now a 4x4)

  • S – Inline-six engine (now 355ci V8)

  • 20 – Series 30 3/4 ton

  • D – Wide side pickup

  • Z – Fremont (California) assembly plant

  • B – 1968 model year

  • 13971 – Sequential production number

Modifications

• Exterior and Structure:

  • Factory frame and body disassembled, sand-blasted, and primed

  • Repaired "dime-size" rust hole behind driver’s door

  • Repainted underside

  • Relocated gas tank to rear with filler in the bed

  • New bumpers and windshield installed

  • Aries Automotive step bars

• Interior:

  • RASTP racing‑style steering wheel

  • Classic Instruments electronic analog dash cluster with 140‑mph speedometer, 8,000‑rpm tachometer, clock, and fuel/volts/temp/oil gauges

  • American Auto Wire wiring harness

  • Patterned cloth seat cover

• Powertrain/Drivetrain:

  • 1978 Chevrolet 350ci small‑block V8, bored .030” over to 355ci

  • 24cc dome pistons

  • 12:1 compression

  • Double‑hump heads with 2.02 valves

  • Holley 650 Double‑Pumper mechanical‑secondary carburetor

  • Electric fuel pump replaced mechanical fuel pump

  • Aluminum radiator

  • Electric fans

  • Rebuilt 1978 GM Turbo‑Hydramatic 350 (TH350) three‑speed automatic

  • Original 2WD converted to 4WD with NP205 transfer case

  • GM 14‑bolt rear axle, GM 10‑bolt front axle

  • 3/8” thick‑flange performance headers with aftermarket exhaust system

• Suspension/Brakes/Wheels/Tires:

  • 6” suspension lift

  • 3” body lift

  • Hydroboost power brake system

  • Cooper Discoverer STT 33x12.50R15LT raised-letter tires

Documentation

• Various parts receipts accompany the sale

Known Imperfections

• Front driveshaft removed (included with sale); needs to be lengthened for lift

• Engine has a rear main leak

• Chips, scuffs, and scratches on the tailgate

• Rust spot on edge of hood above passenger headlights

• Floor liner under the pedals is torn, some pieces are missing

• Floor paint shows imperfections

• Driver door sill is dented and scraped; paint chips on passenger door sill

• Blue vinyl upholstery is worn/torn

• Sun visors are worn; the passenger side vinyl is separating from the visor

• Radio has been removed, leaving installation holes in dashboard

• Courtesy light above rear window is missing

• GMC badges have been removed (but are included)

• Trim around dashboard gauge cluster is cracked on lower right corner

• Glovebox door is worn and paint is chipped

Ownership History

The seller of this 1968 GMC pickup reportedly purchased it as a barn find in September 2010.

Included Items

• Some parts receipts

• Front drive shaft

• GMC exterior badges

• New radio antenna

• Additional parts

• Boxes for Classic Instruments gauge cluster and American Auto Wire

Additional Information

The seller states, “This is a very solid truck... The metal is in great shape. I had only one small rust hole the size of a dime on the driver's side cab corner, but I fixed it... The engine is a new build... It's cold blooded, but when it gets warmed up, it runs great and idles well.”