I'm no mustang officionado, but, there was a version called the California Special that would scoot pretty well. Some of them had 428 big blocks. I can't tell from the pics if that car might be one. It is about the right age, but, I don't know enough and the pics aren't clear. If it has ducts behind the doors, then it might be pretty fast.
I think the side stripe and ducts are clear indicators of whether or not it is a California Special.