NAPCO is the original 4 wheel drive conversion that GM moved in-house in the mid 50's, they used corporate axles and the front and rear were the same ratios or very close, no doubt like anything else back then, a buyer could specify what they wanted even if it wasn't a normal RPO [numbered regular production option]

Bill

Moved over to the Passing Lane

"When we tug a single thing in nature we find it attached to the rest of the world" John Muir
"When we tug a single thing on an old truck, we find it falls off" me
Some TF series details & TF heater pics & Rust-a-holics Unanimous parking lot