It is stamped on the frame of the car in the engine compartment. Under the intake manifold there is a frame member that slopes down and forward. It's stamped into the top of that frame. The number should match what's on the riveted number place. On earlier cars the number plate is on the right upper part of the firewall, often hidden behind a cutout, removable piece of the firewall material. On later cars it's on the left door pillar.
