Few vintage American pickup trucks are more notorious than the classic Chevy/GMC Napco 4×4. Produced from 1955-1959, these 3100-series trucks could be ordered with the Powr-Pak 4×4 Conversion option. This four-wheel-drive system was created by Northwestern Auto Parts Company (Napco) and allowed GM to sell the first production-scale half-ton 4×4 pickup. Some trucks were converted on the assembly line while others could be upfitted at the dealership.
The Napco option — with a retail cost of $995, not including labor — extended up to two-ton GM-manufactured trucks as well as Suburbans and panel wagons. The conversion required only four holes to be drilled and took about three labor hours. Napco used GM brakes, wheels, springs, shocks and OE other parts so that dealers could easily service the trucks.
The original assembly-line Napco configurations were limited. Chevy models were only available with the I-6 engine and four-speed manual transmission; GMCs models offered factory Napco 4WD downstream from a V-8 and automatic transmission. Alternately, customers could buy any GMC or Chevy off a dealer’s lot and have it converted with the Napco Powr-Pak 4×4 kit.
In the 1960 model year, GM introduced a new 4×4-specific chassis and brought production in-house. Napco continued to provide 4×4 conversions for heavy-duty/commercial vehicles before the company was ultimately absorbed by Dana.
Legacy Classic Trucks has revived the Chevy Napco 4×4 through its new tribute truck. “We’re honoring the tradition while taking the truck into the next century,” says Legacy Classic Trucks founder Winslow Bent. “This isn’t a restoration. Each Legacy Chevy Napco Conversion is completely rebuilt with all-new components.”
The process begins with a 1955-1959 Chevy/GMC 3100 donor vehicle. Then Legacy Classic Trucks combines tried/true mechanicals based on their years of reviving Dodge WC Power Wagons. Options are added to suit customers’ tastes.
Legacy retains as much of the original sheetmetal as is feasible. Reproduction body parts are used where necessary. The standard Legacy Chevy Napco 4×4 comes with a classic Stepside box; Legacy uses the larger Fleetside bed on request.
The foundation for the Legacy Napco is a new, fully boxed TCI 2×6-inch frame. (The original 2WD frames weren’t designed to withstand the stresses imposed by modern engine power, oversized tires, and power steering.) Legacy works with law enforcement to legally transfer the frame VINs from the donor chassis to the TCI units.
Then premium components are added. Legacy co-engineered the suspension with Alcan Spring and Chevy 4×4 specialist Offroad Design (ORD). Custom Alcan leafpacks optimize the ride but preserve some of the classic road feel. The front springs offer 10 inches of travel. They are mounted over the axle and incorporate the ORD shackle-reversal kit. By moving the shackles/pivot points to the springs’ aft ends and solidly mounting the front ends, steering and cornering are crisper.
The rear Alcan leaves provide 11 inches of suspension travel. To compensate for varying loads in the bed and control weight transfer, Legacy uses an adjustable Currie Antirock Sway Bar. This helps keep the rearend firmly planted, particularly when the bed is unladen.
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Ride quality is fine-tuned by premium King remote-reservoir shocks. The front 2.5-inch-diameter units have 12 inches of travel, and the rear King 2.0s handle 14 inches of suspension travel. Legacy Classic Trucks tunes the King shocks for each specific Chevy Napco before delivering the truck to the customer. A final suspension detail is King Air Bumps. They save the springs from overflexing by cushioning the impact should the suspension bottom out during enthusiastic driving.
Axles are stout Dynatrac ProRock units with disc brakes. Legacy used the Dana 44-based ProRock for its prototype Chevy Napco but will step up to the ProRock 60 for production trucks to optimize the front driveshaft angle. Detroit Tru-Trac limited-slip differentials and 4.11 gears are standard. Other performance differentials such as the ARB Air Locker are available by customer request.
The front Dynatrac ProRock received Reid Racing knuckles to accommodate crossover steering. The custom Legacy linkage is paired with a PSC performance steering box and pump. Premium Warn manual hubs maximize front axle component life when free-wheeling and positively lock in four-wheel drive for high traction situations.
The axles turn Toyo Open Country R/T all-terrains. The Legacy Chevy Napco uses period 16×7 steel wheels with hub caps inside 33×10.50R16 Toyos as standard equipment. A harder-core upgrade is 34×11.50R17 Toyo R/Ts on 17×8.5 Trailready HD17 beadlocks.
Legacy Classic Trucks tested various powertrain combinations and settled on a choice of two engines that provide an ideal blend of power and durability. Standard issue is the 350-hp GM 5.3L Vortec LC9 V-8. The alternative is the 430-hp 6.2L LS3 V-8. To curtail any cooling issues, Legacy uses a racing-style Ron Davis radiator.
Customers also get a choice of exhaust systems. The base setup is a Borla 2.5-inch stainless steel system with dual mufflers and quad tips. The premium system adapts Borla’s selectable 2.75-inch C7 Corvette Stingray NPP kit. This system has valves in the mufflers and allows the driver to choose between Quiet and Sport modes at the push of a button. Alternately, customers can choose a receiver-hitch option with a traditional Borla side-exit exhaust.
Most customers opt for the the GM 4L65 four-speed automatic transmission, but Legacy also offers the AX-15 five-speed manual.
The transfer case is the legendary Advance Adapters Atlas II. Standard low-range gearing is 3.0:1, but other gearing options are available for owners who want to crawl slower. “The powertrains are set up for the truck,” Winslow Bent emphasizes.
All Legacy Classic Trucks are built to order. The standard Legacy Chevy Napco “Black” interior package uses Horween leather upholstery, rubber floormats, and a Nardi black-leather steering wheel. Customers can upgrade to Legacy’s Sandlewood package, which incorporates a suede headliner that compliments the Horween leather upholstery. Attention to detail includes a mahogany Nardi Torino steering wheel and premium Mercedes-Benz square-weave carpeting.
Other available amenities include the classy Classic Instruments Task Force gauge cluster, a Vintage Air HVAC system, and a 900-watt sound system that starts with a period-appearing Retro-Sound head unit, which feeds a Focal amp and K2 speakers plus two 8-inch JL Audio subwoofers.
The exterior is also customized to order. In addition to bed configurations, customers have a choice of three front grille styles: 1955-1956 cross-hatched Task Force, toothy 1957 Task Force or 1958-1959 small-grille/dual-headlight Apache. Legacy offers five standard paint colors and an up-level two-tone accent package with Pepper White roof, back panel, door panels and lower dash. Custom paint is available at extra cost.
“We’re excited to revive interest in the Chevy Napco, which I think is one of the greatest trucks of all time,” says Legacy Classic Trucks founder Winslow Bent. “The Legacy Chevy Napco Conversion combines the personality of the original Napco with modern performance and handling. Like our Dodge Power Wagons and Jeep Scramblers, the Legacy Chevy Napcos are hand-built by craftsmen in our shop near Jackson Hole, Wyoming. We use our trucks hard here, and we’re confident that our customers will enjoy theirs as much as we enjoy making and testing them.”