From Max wedge site.
The build Broacast sheet was paperwork that followed your car down the production line describing the options to the assembly man. It is like pedigree paperwork for a pure bred dog.
The most common places to find build sheets are:
In the seat springs of the rear seat back cushion
In the seat springs of the rear seat bottom cushion
In the seat springs of the front bucket seat backs, behind the plastic or metal seat back cover
In the seat springs of the front seat bottom cushion
Under the carpet, commonly on the driver's side in front of the front seat, but I've found them on the passenger side (common with Hamtramck cars) and under the rear compartment carpet (commonly on the driver's side with St. Louis cars and later M-body and F-body cars, though I've seen them on the passenger's side as well)
Taped to the top or the back of the glove box liner
Taped to the heater core under the dash
The most uncommon places to find them are:
Stuffed in the headliner above the driver's seat (found in a St. Louis car)
In between the gas tank and the rubber gas tank mat (Los Angeles car)
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