When I removed the fuel tank I found a thin strip of a build sheet that was protected from the mice by a mounting point. About all I could tell from that is the car origninated in Kansas and was shipped to Will Motors in Mapleton MN; about 15 minutes south of Mankato MN.
When removing the back seat to clean and detail the floorboards there was somthing sewn into the seat vinal mounting seam. It turns out this was another copy of the buildsheet, this one about 90% complete. This is documentation of the original SS assembly of the car. There are things listed like "Stripe kit", F41 suspension (swaybars), and the "Z15 SS Group" option. The car was built with a 350 4bbl engine. Some of the pictures here will click to enlarge.