I am upgrading to a new 25ooHD from a 2015. Does anyone know if GM used the same frame for the 2018 as was used in 2015? I have a PullRite super rail system under the bed that I want to move to the new 2018 and want to make sure GM did not make any frame changes. These 5th wheel systems are NOT cheap and I do not want to have to change out everything from top to bottom.