Well, the fact that either the guy actually has no clue about Mustang History or is trying to pull a fast one is what bothers me the most.
I do agree also that the install actually looks kind of clean, and assuming that maybe the roof was previously detroyed by say a standard sunroof or something that totally does not belong, than I would say it is quite possibly the lesser of the evil options available. Not the worst idea I've seen anyway, but yikes it must get hot in there at high noon just about anywhere in the country. If it had a very dark black tint to it and the trim was painted body color instead of chrome, I'll bet it wouldn't look all that hideous.