the same chassis doesn't necessarily mean that the same body panels will fit. With fords however that usually is the case. Although the sn95 and new edge body styles do not compliment one another; one is soft and curved while the other is hard and sharp. Yes the body panels will be able to be swapped (hood, front bumper and fenders), but thats basically it (not including wings/spoilers). On the s197 platform there is a whole lot more you can do. you can have an early model s197 (05-09) and swap the entire front to look like a mid model s197 (hood, fenders, bumper from 10-12) and it look completely normal eventhough its a mid/late model s197 front because the lines match. Also with 10/12 and 13/14 you can swap the rear bumper/trunk/lights to use the leds that people charge up the butthole when selling. Like evilcw311 pointed out there are parts made by cervini, vis, abc, etc that will fit the 94/98 body style, but look like the 99/04. So are parts able to be swapped? Yes. Does it flow? Eh, not so much. Ricer? Getting there. Eye sore to most people? I think so.
But if that is something you want to do then go for it and we can help you out. if you want to learn about all there is to know we can teach you.