Well, you could try scraping the paint off with a plastic scraper, or mild solvent. If that fails, or the tag (and door) is not original, send the VIN to Kevin Marti. Then you'll know pretty much whatever you'd want to know about the car.
ford used to offer a brief history based off the vin. Not sure if they still do.
I cannot remember if it is a history 999 report (thats stuck in my head). but you call them, give the vin. Then they mail you a free report a few weeks later. IIRC, it works for 67 and later vehicles.
Finally got my "History 999 Report" from Ford today! You can see the contents of it below.
Want one? Call Ford Techical Service at 1.800.392.3673 (USA only). For those of you in Canada, the number is 1.800.565.3673.
Dig through all the menus until you can talk to a represtative and ask them about a "History 999 Report," and if they don't know what that is call it a "Buildsheet Report."
They will need your VIN#, make, model and some personal info (like address and telephone number). I think info is available for 1967-1996 models. The report is free.