Monteverdi Sierra quircks

I'm still doing a little research regarding the front seats used in the Monteverdi. It's still unclear if they are BMW E3 or E12 seats. At least they are not recognized on the E3 FB forum. Typical.

In any case, I noticed something remarkable. When going through the photo's on the forementioned website I spotted this Sierra which still had the Original Dodge Aspen seats, the long low headrests are clearly visible and no headrests in the back either.

Dodge Aspen seats:

And another thing that was remarked on the FB forum was on the following photo (this is the one that was for sale by Aaldering, the Gallery in the Netherlands). Someone spotted the manual windowslider.

According to this auction advert there has been 2 or 3 Sierra cars delivered without power windows:

https://www.dorotheum.com/en/auctions/current-auctions/kataloge/list-lots-detail/auktion/10057-vintage-motor-vehicles-and-automobilia/lotID/420/lot/1515994-1977-monteverdi-sierra.html

And another remarkable find in the same gararge is this car. Potential the only Sierra delivered with a 5.9 Engine. As far as I'm aware only the Stationwagon and the two cabrio's were equipped with the 5,9 engine.