First, I was wrong in stating that 6S001 was "the only 1966 GT350 to have a pony interior from the start." In reviewing the photos I have of 6S023, it's clear that car also had some pony interior items. Door panels and handles at the very least. And it might have come from San Jose with pony seats, but if so, they were swapped for standard seats before any photos were taken.
So, it looks to me like this car has to be either 6S001 or 6S023, primarily because of the pony door handles & panels; although there are a few other clues that I won't go into at this time. And both 6S001 & 6S023 should have been at S.A. LAX in October, 1965. The determining factor is whether 6S001 had the blue vinyl top in October, 1965. If yes, then this car is 6S023. If no, then we may never know for certain which prototype this car is. I'm working on finding out when 6S001 got the blue vinyl top.
So, it looks to me like this car has to be either 6S001 or 6S023, primarily because of the pony door handles & panels; although there are a few other clues that I won't go into at this time. And both 6S001 & 6S023 should have been at S.A. LAX in October, 1965. The determining factor is whether 6S001 had the blue vinyl top in October, 1965. If yes, then this car is 6S023. If no, then we may never know for certain which prototype this car is. I'm working on finding out when 6S001 got the blue vinyl top.