Will the 2018 mustang headlights and fog lights fit the 2015-2017 mustangs

You will have to change the fenders, hood, and front bumper for them to fit. They changed the shape of all three of those things to conform to the new shape of headlights. It has been done before, but it wasn't cheap. This is a 2017 Mustang GT with the conversion done. http://img.photobucket.com/albums/v482/jkr40/34419194_10107331319194600_6572243275137155072_n.jpg

Hello, You will need to address this concern through experimentation. You are likely going to be one of the first to try it, so post it online to let everyone know how it goes and what you find.