redman1401 said:
Looking at the photo of the pickguard off the body, i can see a "66" on the pickup so yea i'd say its legit, or a really REALLY well done relic job.
Agreed, the final consensus is that is extremely likely that this is a real 1966 Mustang. As HNB pointed out, the dates on the pickups match and everything else on the guitar seems to be typical of that era of Mustangs. And as redman said, it is technically possible that this was relic'd to appear vintage, but it is highly unlikely that someone would remember to replicate every last little detail like that (i.e. the date on the pickups, etc.) As much work as it would take, they would have forgotten something.
I would bank on it being 100% authentic. It is really a sweet little guitar that looks like it has quite a history and story behind it. It is also a transitional Mustang, as 1966 had CBS just getting solid feet on the ground with Fender Guitars. I wouldn't be surprised if some of the parts on this guitar are from pre-CBS Fender surplus.