Well, I just talked with an individual from Rancho. This is them! We discussed the kit and the issues I had. WIthout them actually seeing the kit while it was on my truck, we cannot pinpoint the highway speed isues, but it was confirmed the rim set up was a large part of the issues with the knuckle/ caliper spacing. The wheel spacer with spline nuts also could have been part of the issue. The individual I talked with was even willing to have the kit reinstalled at their facility at N/C to make things the way they should be. (too bad I'm a few states over).
If you have questions/ concerns he's more than willling to talk with people. Send him a PM.