Take a look at these. Alcan Spring - Manufactures Fine Custom Leaf Springs
If I didn't already have lift springs I would probably go for these. If I decide to change my lift springs, I will probably go for these.
Tailor made for you truck. They know the 4runner so, maybe not so tailor made...but they know the right formula for what you want based on your needs.

Or these? With stockish springs and these to give flex. Teraflex Revolver Shackles | TeraFlex Suspensions But there is debate as to the dangers if they unload unexpectedly. And when they unload and you droop into a hole, it's said that there is so little weight that you don't increase traction.
Maybe I haven't searched hard enough on this myself, but most accounts seem to be arm chair theories, and not accounts of people who have had horrible roll over with them. So, not sure what to think.

But the Alcans would be good at a stockish height with the orbit eye to give you even nicer flex.