Thanks all for the ideas. Let me through this out there too.
If I'm running down the road with the cruise on, the vibration feeling (although pretty slight now) is very constant. That said, if I go up onto a bridge or something where there's a pretty decent bouncing feeling from going from pavement to the bridge, while the car is "floating" over the bumps, for just a little bit of time while it feels like it's not as heavy on the tires, it feels 100% normal and smooth. As soon as the truck settles back down to normal riding and not bouncing from the differing road conditions, it's right back to the vibration.
Not sure if that makes sense or helps at all.