Rob, I played around with King Springs and even 'keeper springs' to ensure that on full droop they had correct/some tension. A critical factor is the length of the spring in relation to the shock and suspension travel. You want the shock to operate over most of its range, not be wound right up because the spring is too short.
There may also be a front to rear difference in spring and shock length, depending on your suspension set up. My springs are more vertical now than before and that changes the equation again. As Ben has said, I would have a chat with the guys who have the same suspension. I have my old King springs, if you want to play around with them.
If you don't want to deal with Summit, try The Car Shop in Moline. I found they were cheaper on many items and gave great service and advice. (
High Performance Parts & Accessories - Car Shop Inc. )