Driving my truck it vibrates when driving 55 MPH or higher what is the cause?

My first thought is Tires; Could be something in the front end with wear. Is there someone you know that can check this for you.

My stepdaughters car did the same thing we replaced the tires and the motor mounts and it still did it we changed the front struts and the problem went away

Start by having the tires rotated and balanced.