I beg to differ. Let me share you my experience that I had and witnessed in person

I parted out a 1968 Dodge Coronet 4 door. And yes everybody(most) knows that the bottom seat is different than a 2 door version, they're more rounded off at the corners. As for the upper seat, I've asked online the same question about it being the same for a 4 door & 2 door. I never got a clear cut answer, just people speculating that they would be the same. So the opportunity arrived for me to find out myself on my own.

I took the upper rear seat from the '68 4 door over to my '68 Charger to see if it would fit. It did not. The bottom loops that catch the tabs surpassed them quite a bit going towards the floor board. So it dawned on me like other interior related parts, that 4 door stuff is taller and/or longer. A-pillars, windshields, wing windows, windshield trim and now rear upper seats.

So from my personal experience the answer is NO that the rear seats from a 4 door (both upper & lower) are not suited for a 2 door version.