Jonathon,
The resto-pack is not specific for a particular vehicle. In other words it is NOT a build sheet for a single vehicle. It is simply a collection of technical documents and specifications for all models of trucks for a particular year. Whether or not you had the production number would not matter, you get the same package of materials regardless of the vehicle production number. If you want a resto-pack, just make up a 5 digit production number to add to your ID number.
Keith Hardy has a copy of the
1939 Car and Truck Specifications (the 'restoration pack' for 1939) online at his
Old Online Chevy Manuals page.