i tried to put a 02 v6 front bumper on my car once and it didnt fit.. but it was close... so maybe with the fenders, headlight panel, bumper and headlights it might fit.. you would also need a hood ..
most likely your going to be dissapointed if it did fit.. i dont think it would look right..
I believe the parts will fit if you use the 99-04 fenders along with the bumper. But the body lines are gonna be way off. There was an article in Muscle Mustang a few years ago about a shop that put a 99-04 body on a 95GT. The article stated that it was NOT very cost efficient. The owner had more money in it than he could have bought a 99-04 GT for.