What you are describing does not sound like a state-initiated VIN change, as the VIN on your title is still in a valid Ford format. The driver's door should have a tag with the VIN listed. Does that match the dash VIN? If not, and the door VIN correctly matches your car, then probably what happened is somebody had a cracked dash pad, found a good one on another car, and rather than switch just the pad portion, they replaced the whole top dash, metal and pad. With that metal piece came the VIN tag. If you read the door tag, it will say "not for registration purposes" or something similar. I believe the government required the placement of the VIN on the dash starting in '68, and this was to be the "official" VIN? Problem was, they weren't too permanent.
Your homework: compare the door tag VIN with the dash VIN. Also, as stated earlier, check for the buck (build) tag on the passenger side radiator support (facing the headlight bucket and front of the car). If present, there is a VIN stamped on that as well. Compare that to the dash VIN too. If you provide the proper homework (ie, how the letters and numbers code out), you may wind up with enough proof to get your car VIN corrected properly. Then again, it may not be possible at all, and you have to go with a brand new, state generated VIN as Hemi states.
Good luck, and let us know what the door and buck tags (and as a last resort, the fender apron) VINs come out to be.
1971 Grande - 351C - C6
1973 Coupe - 351C - FMX