For less than the cost of 'real' GT5-S seats, you can have your original seats reupholstered in wrinkled-leather with reworked padding etc. and avoid head-clearance issues. The real GT5-S seats have a reclining feature that is next-to-uselass in the Pantera, & a very thick padded seat and back. IMHO, the best seats for the Pantera for looks, long-distance comfort, price and ease of installation are OEM early 3-piece seats, with the following mods:
1)- slot the back straps & add knobs to the stock allen bolts, so seatback rake can be altered.
2)- reupholster in wrinkled leather, your choice of color
3)- re-contour the rear seat crossmember; in some seatback positions, this steel piece causes butt-numbness on long runs.
4)- add nylon seat rollers for ease of adjustment back & forth.
In my '72L, this cost $700 a pair (in 1990; more now), resulted in far more comfort than before, dropped the seat bottom 1-1/2 inches so I now fit comfortably wearing a helmet (I'm 6'2") and quickly adjusts for my 5'4" wife as well. And they bolt into your car with no fabrication. Most of the Pantera vendors offer this service. Other than this, consider dropped floorpans to compensate for the thicker GT5-S seatbases.