2011FX2

I have a 2011 FX2. Installed level kit new wheels and tires. Truck rode fine. Added rear blocks.... truck still rides fine. Had to swap out wheels for new set and now around 45-60mph truck shakes like wheels are out of balance and when going over pot holes steering wheel seems like I can feel something loose. I took it to another place to have tires rotated and re-balanced. Truck still does the same thing.... no change? Any idea what this could be? Alignment?....although still drives very straight. Shop stated wheels were pretty balanced to begin with.
I'm ready to give up and drop it off with Ford and see what they can find??