If you need a cheaper solution, not saying not to buy a factory type air seat but the can go over five thousand each, take the old Morgan sports car route.
Morgans were wood frame roadsters, had a 4+4 years back. Anyway, the seat is really a cushion type with a zip-out back pocket. An inner tube like used on a bicycle and it was folded with an arch in front or under your legs and serpentine under the butt. Just blow up the pressure to firm it up or let the air out, very comfortable when you get it conformed to the old body.
This arrangement is much better than those cheap mini inflatable seats.
Might use the existing seats and upholster in such a fabrication. The larger the tubs the bouncier seat you'll have and this can get real bouncy, too much so if over inflated, you'll bounce off the roof. Smaller tubes as in the Morgan were a nice ride even over dirt roads on a rally.
No one will know you're riding on air.
Now, the real seats have a rebound feature as you know, you pay for what you get.
