In re-reading these old posts, it reminded me of one car in which we added dropped floor pans by only cutting the two sides and back of the seat floor, then bending the stock pan down and welding in triangular filler pieces on sides & a rectangular one in back. That retained some fore-and-aft adjustability for the owner who was a big man! Combine this with seatback rake adjustment and you have a definite improvement for larger adults.
Also note that post-Ford '80s-up Panteras are rumored to have different floor pans from the early cars, which provides factory dropped seats (and dropped battery boxes, too). I've driven the late models but never had one on a hoist to examine the floorpan design. Finally, if you can live with slightly more road noise in the cabin, cut away the rug below the seats, remove the aluminum rug spacers below the adjust rails and bolt the rails directly to the steel floor. That lowers the seats by almost an inch with no welding. Note in any case the floor MUST be flat or the adjust rails will bind and fore-and-aft adjustment will be very difficult.