There should be one in your car, I think it's attached to the main wiring harness. I was working on the drivers door mechanism on my 68 Merc and found it in the door. Old, yellowed and faded, but still legible.
Yep, I found one taped to the wiring harness behind the instrument panel. Extremely brittle. I also had one taped to the back of the drivers side door panel. I think some have even found them under the carpet (but good luck on that). Marti reports don't go back to '66, they start at '67. For some crazy reason Ford didn't think it was a good idea to retain those records until '67.
I tried Marti's already, and they can't help. As for finding a build sheet in the car - no hope. Whoever had it before me has gone through it and removed everything. I've heard of them being under the rear seat too.