Yesterday I was looking at a 03 gt at the junkyard (the rear disc setup). I don't see why I chouldn't use the braket mount, braket and cliper on my fox. Will someone who knows about this please comment. Posted via Mobile Device
Mike is correct, (as usual!) The axles and rear end housing on the 03 are too wide for your Fox 8.8 rear end. The 94-98 axles are longer than the Fox axles, but will work with the disc calipers and brackets just like on the 94-98 cars on your rear end.
If you by chance have some aftermarket 5 lug axles you want to keep, you can use special brackets or modify the stock brackets to mount the 03 parts on your Fox axles. We can point you in that direction if you need the info.
The custom brackets can be bought from North Racecars Cobra Replica and Mustang Parts Connection for about $150 or from my friend, Neighbors is his name on here. He sells behind the flange mounted brackets on ebay as Neighbors_Industries for about half that.