The best seat to use in a Pantera is a Pantera seat. That's why they were made for the car.
The original upholstery is the main culprit to them though. It made them hard and somewhat non conforming.
What Hall did with recontouring them into the later 80's configuration makes them 1000% more comfortable.
I have lowered floor pans and the pedal assembly spaced 1-1/2" forward. I'm 6'2".
My pans are dropped 2". I had to space the seat up so I could see over the dash.
I can virtually recline and added power seat platforms which help with the height adjustments as well as seating position.
If you asked me, I'd tell you to do all this and forget about searching endlessly.
The best fitting aftermarket seat that I experienced is the Scheel but that hasn't been made in 20 years.
The Hall seat is better.