At some point in the last 20 years, four-wheel-drive became common on new light trucks while manual gearboxes and dash-mounted ashtrays became a rarity. But in the days following World War II,
General Motors did not offer a factory-built four-wheel-drive pickup truck, so a small vendor called NAPCO, or Northwestern Auto Parts Company of Minneapolis, Minnesota, stepped up to meet the demand.
Armed with NAPCO’s ingenious Powr-Pak 4×4 conversion kit, a mechanic could transform a two-wheel-drive GM truck into a four-wheel-drive in just a few hours, with no welding and minimal cutting needed. The front drive axle in the package was fitted with tubes modified for constant velocity joints, thus allowing the wheels to steer, and the transfer case was a divorced unit, driven via a shaft off the transmission, so it could be mounted without altering or adapting to the stock powertrain.
NAPCO conversions date at least as far back as the 1947-’55 (first series) GM light trucks. However, prior to 1955, only one-ton and three-quarter-ton trucks could be converted, because half-ton trucks used a torque-tube style driveshaft that wasn’t easily adapted to a transfer case. Once the torque tube was eliminated, in the second-series 1955 trucks, it became possible to use NAPCO conversion kits on half-tons.
This GMC 3/4 ton(called the 150) is believed to have the original Napco 4×4 system and is powered by the inline 6, mated to a 4 speed manual transmission. The pictures say it all, you’ll be hard-pressed to find a nicer GMC of this era! Purchased by the current owner in 2001, they spent over 16 years on the restoration, going over every detail.