I saw an 87-93 GT on the Woodward Dream Cruise 2007, that had side pipes. The only reason it looked good...(actually GREAT)....was because he used a Mustang GT rocker molding and molded in an oval shape cut out for the pipe. It looked just like the oval in the 94-98 SVO side rocker moldings.
If you had a GT I would do it using the rocker moldings, but if you are just going to bolt them up with no molding, I would say no! Also, GT moldings on a coupe/notch will not look good either.