So after driving the truck some more, I think the spring rate is a little higher than I would like. For someone who does high speed off roading frequently, or prefers a firm ride with enhanced handling, I think the 650 lb coil would be perfect. I however, drive around town and highway a lot, so I think a lighter spring may suit my needs better.
I talked briefly with a Bilstein Tech, as was to be expected, he couldn't give me recommendations on this setup due to liability and the fact that they haven't tested it (no one has). He did however confirm that the 1st gen Tundra 6112 uses a 650 lb spring, and the 3rd gen 4runner uses a 550 lb spring. A little more research showed that the 2nd gen Tundra Trd Pro uses a 600 lb spring.
Now, I'm not sure why they chose the 650 lb spring for the 1st gen Tundra that weighs less than the 2nd gen Tundra.
So with all of this information, I think I have decided to swap to a 16 x 3" 600 lb coil. We'll see how that goes.