[Hutch]

Jeremy_5
The early Napcos were standard trucks that were sent out to be converted prior to 1957
The front axle should have a stamp on it saying NAPCO like this one
The first year for the in-house conversions was 1957.
The kits were designed to be installed with no modification other than some holes drilled in to the frame, this way you could put the vehicle back to its original state and then move the converion to your new truck.
The only way to tell a line built truck is the crossmember had rivits instead of bolts.
There should be a way to date the conversion with numbers off of the components.
I had a 1957 napco for a while during the late seventies.
Here is a pic I took of it around 1977