Well, I can say this much, the switches are not original, in 1966, Olympic White Mustangs had white switches and white pickup covers. Someone probably needed to replace them at some point and the only color availible was black.
The neck joint looks a little dodgy too - looks like a refinish job from here, but I'd have to look inside to know for sure because on Fender's the paint can and sometimes did creep into the neck slot of the guitar around the edges (with a bare wood middle where the paint stick was).
I'll say though, that's the cleanest 66' I've ever seen hardware wise. And that IS indeed a vintage Mustang vibrato unit on it and all the proper vintage hardware. I had a 1966 myself that was originally the same color as yours but whoever owned it before me painted it gold/red/metallic turquoise. Sadly I had to sell it for medical bills and now some chop shop in Seattle has the body and parted it out (rolls eyes).
