This is one gorgeous Avanti by anyone's standards. I think John has presented it beautifully. But for a car that is expected to fetch top dollar, I don't think pointing out that the seats appear to not be the ones the car was built with, is "nitpicking". A buyer expecting an as-original car, who is willing to pay a price commensurate with that, should be aware of this type of thing. Of course, he might not care, but I think John would agree that "original" brings the most money.
According to the Oct. '87 article on Avantis by Fred Fox in Turning Wheels, thick seat backs were first installed as standard equipment on serial no. R-5361--way before this car. The two-tone interiors were gone by this point too. It certainly could be that either the dealer or original owner thought black seats would be a nice contrast and had them switched. One would think if the owner requested this, it would show up somewhere in all the paperwork that appears to be with the car. I'm curious as to what the build sheet shows for interior trim.
I think "nitpicking" is what is done to a car that isn't presented as perfect or is expected to fetch a not-huge price. Asking the questions on a car expected to bring top-dollar is just logical...the prospective owner should know, even if he doesn't care.
Bill Pressler Kent, OH