This is all I can find for now,
"If they are the stock springs they will just have a couple lines on the end, looks like II (.27) or III for the heavier springs. Most aftermarket will be marked with the actual spring rate."
If you have a shop nearby they should probably have a spring tester and tell you exactly what you have.
I'll stop back later, & let you know what else I can find.
Tuck\o/