Every replica manufacturer varies to some degree some where. ERA is indeed right up there with the best of the best for an accurate body.
Consider the old 'High Techs', also considered among the best of the best for accuracy (in build specifics as well, often VERY detailed to original specs). My friend has one, beautiful car. We were comparing the ERA one day when he mentioned the bottom of the rear fender flairs on his High Tech protruded out farther than on my ERA. Which was 'correct'? A tough question because even the originals had varying degrees of wheel arch flair in them.
We concluded that the High Tech protruded a little to far, to pronounced. The ERA was a little cleaner, looked better. I had to agree, 'really'...
It is often said, 90% of the people you meet at a car show couldn't tell the difference from one replica to another. I tend to agree, but I don't care about the uneducated 90%. I care about first what I personally see, those seeking more knowledge of what to look for and the 10% who DO know!