Thanks but...I do have aftermarket leaf springs in the car. They are from Mopar Performance. The previous set of springs were probably original. The car was built with a 318 so I figured the MP springs were an upgrade. They were. The car rode firmer and sat a little bit higher. I was just curious as to the way that leaf spring rate is calculated. Obviously a pack with more leafs would have a higher rate, as would one with wider leafs. A shorter segment between the eyelets would be firmer as well. There were some early A body cars that had leafs with unique thinner sections in the middle, assuming that was to reduce the rate while keeping the overall shape the same as with V8 cars?
Anyhow...I was just thinking about this because it makes sense to me that a neutral handling car is achieved by balancing the front to rear spring rates. Of course, the sway bars are factored in to it all as well.