Hello James Kitchener,
May I suggest- You Tube- Ridetechtv- How to Evaluate Your Suspension.
Suggest going to Ride Tech website and selecting "Knowledge".
Look at Strong Arm Dimensions data base that may pertain to your application.
Look at Vehicle Weights data base that may pertain to your application.
Look at Spring Rate Calculator to enter data for suggested spring rates.
Ride Tech will assist you in all this, it's their business. Good Luck. Harry