These engines are not interchangeable, so you cannot just install the 3.9L in the place of the 3.5L. This will require all the computers as well as transmission. Also, the mounting points could be different as well.
This will also need programming after the installation.
The best option would be to find another 3.5L and replace it.
Let me know of any questions.
Monday, August 29th, 2022 AT 9:29 PM