If this is in fact a 12B build (if I'm reading that right?) 2nd week of December 68 would indeed be a short spoiler. So that could be originally applied, but have to see under the decklid for more clues.
Basically would have to see the car in person to make any determination on value for me, but I do agree Bullitt, would be a neat car to go through the drivetrain on to make it dependable, and drive as is to enjoy without worry. Was thinking of doing the same thing with mine. I rarely ever sell any of my stuff so I'm not in the hobby to flip cars and make money, but I certainly don't care to get in over my head on one either when you figure asking price and cost of restoration, then given what ever the current private sale market is on a particular car. That's how I look at it because eventually I'll be too old to enjoy these things and they'll have to go somewhere