Sorry for the delay. It looks like you have done an excellent job of laying out the required dimensions. That along with the axle weights and I should be able to come up with spring rates for you. A couple more things I will need...
Capacity of the fuel tank so I can add in the weight of a 1/2 tank.
What you would like the car to ride like, i.e. soft like a typical American sedan, firm like a BMW, or stiffer more like a race car?
I hope I am not too late to assist you.