I ordered my springs from
Coil Spring Specialties. I provided them the part number from the blue shop manual. We discussed the percentage of stiffness to be added and the front ride height.
I would advise you to first determine what is the present ride height of your car. The manual explains it all. Front ride height is adjusted with the thickness of the rubber on top of the spring. If a adjustment is needed you can order it for any dealership.
Changing the springs is not easy job. By determining the correct rubber thickness before installing the new springs will eliminate the need to take the springs out to install new rubber. Also I have found that forty year old rubber should be replaced. It will help improve the ride.
If you have any questions ask.
When you take the springs off there are several other jobs which should be preformed to greatly improve the quality of the ride.