i read that some guy has a 03 gt rear bumper on a 97 do they fit or did they guy had some custom work done? this is where i saw it: http://forums.stangnet.com/showthread.php?t=407771 check Oldcobraguy's signature on his post
I have seen a sn-95 with a 99+ front bumper but I didn't like it and it took a lot of work. As far as the mounting I bet it will fit, but you will have to mold it to make it fit.