duke,
I've gone through something similar to you, but after reading your statement, there are some things to consider
before deciding on spring rate/s. Because I didn't follow steps 1 thru 4 as listed below, until recently, my collection of springs looks like I have a spring warehouse.
To separate the wheat from the chaff, find out the following:
1. Have you determined your desired ride height, front and rear?
2. Are your shocks the proper length for the desired ride height?
3. Are your springs properly matched to the length of the shocks?
4. And finally, what level of ride firmness are you looking for?
After you determine ride height, measure the distance between the center-lines of the shock mounting holes. Then go to a website such as this one
http://www.carrerashocks.com/pdf_files/street_rods.pdf, and look for your proper shock. Shock compression and extension length is very important. Sites such as the one shown, also recommend a specific length coil for the selected shock.
Hope this helps.
David