Don! Do you have any shipping labels for the rear seat springs? My rear seat has shipping labels from the manufacturer to Chrysler. Is you car produced in St Louis or Detroit?
The first thing I did when I bought the car in Mar 84 was pull the rear seat hoping to find a build sheet. YES! I have carefully preserved the original build sheet. There were no other labels or anything else under the seat cushion or (later) behind the back seat back (I would have saved them if present). My GT is a Detroit-built car and sold in Albany NY (which I already knew from a dealer decal inside the glove box) per Chrysler Historical.
As a side note I did find a seat manufacture's label of some kind when I pulled the rear seat from my 65 Dart wagon (car made in LA and seat label also from LA) - but no build sheet.
Are you coming for the Nationals again this year? We're staying at the Super 8 in Zanesville this year.