I understand, but the original seats in the older cars are some of the most comfortable ever built if re-padded correctly.
The problem with seats from a newer car is in the back seat. The newer car's rear seats just sit on the floor, and are made to fit the floor pan. They are useless in any other car because they have no free standing support. The front seats would be O.K., but that means you need your rear seat upholstered to match the front seats. It's a no win situation.
No one lives forever, the trick is creating something that will.