The front and rear track is wider than the stock fox based Mustang.
The rear axle is 3/4" wider per side and you will have to replace the master cylinder and brake proportioning valve to accommodate the rear disk brakes.
The front track is also wider, and may cause the tires to rub on the inner fenders. The fox steering rack may need to be changed for the 96-98 model steering rack due to the wider track.
See 87-93 Mustang 5.0 Brake upgrade pages. Improve your 60-0 times! for the best and cheapest brake upgrades and 5 lug swaps. The site doesn't sell anything but some fittings, but the tech notes are great. It tells you what junkyard or remanufactured parts to use to upgrade your brakes. It has almost everything you could want to know about Mustang brakes on it.