...build sheets may not always be in the car.....behind the rear seat back, or under the rear seat are very common spots....sometimes under the carpet, over the glove box, in the seat backs on the front seats.....virtually anywhere it seems...
...the "matching number" is stamped on a flat pad, on the engine block, just above the oil pan on the passenger side of the car....it will normally be the last 8 digits of your vin#....it can be seen with the car sitting flat, but it is easier if you raise the car a little...