will a 4.6 fit in a 95 where a 3.8 comes out

Hello Putting a Grand Marquis engine in a Mustang may be a bit risky, due to different exhaust points and cams. I'd also be nervous in switching out cylinder count from different engines. Of course, anything is possible. This would be a tough job. You can almost always adjust an engine to make it fit, but this would be time-consuming and may not work. Best of luck CarGrrl