Just picking a seat isn't going to solve the problem. There are other factors involved.
Most likely what works for me may not work for you.
It depends on how your body fits, not mine.
I've always said that the best seat for a Pantera is a Pantera seat.
I do think that the post 1974 USA seats are better and for me, in leather with the hinged back are best but I don't think that it stops there.
Everything else is involved as to how YOU fit into the car.
That includes the seat tracks, the steering wheel and the pedal positioning.
I don't think that you can wave a magic wand and with just the seat pick fix everything.
My solution was quite involved but it does allow for easy adjustment for other drivers without the trauma.
ALL of these "GT" cars have issues with seating comfort. Some seats from non-Panteras will work for YOU. Some will not.
Aftermarket wise, the discontinued Scheels fit well but made you fit in one way just like in a F-16 and are questionable for long drives. YOU have to fit the seat. Not the other way around.
I didn't like the way even the fabric held me and kept me from squirming around to adjust myself. Size wise thought they were very, very good.
So unfortunately there is no simple answer to this question. It is somewhat of a project and it will become a solution for just one driver in MOST cases.
I didn't accept that and made everything easily adjustable. It was much more then just the seats.