If your car has six leaves (if in doubt, just count...) it will have a harsh ride, but on the other hand they will have more resistance against old age and sagging. So the first question is if replacing the springs really is needed. The answer would depend on age, mileage, visual signs of sagging plus how you feel the suspension is performing. With 25 years and perhaps a substantial mileage it may well be that a change is due. What is recommende by most is the four leaf springs intended for the four seater, which is said to be a good compromise between softening up the ride and being stiff enough to ensure a good handling.
My car has six leaves and a quite harsh ride, and I have driven a four-leaf 4/4 with two people + luggage which I found way to soft. So when the day comes, I will try to compromise by searching for four-leaf springs, but with the added stiffness from the spring intended for the four seater.
