Ummmmm the only rearend that came stock with disc brakes in a fox body stang was the 93 Cobra, so unless this is some sort of aftermarket swap then no it wont just be a bolt in affair.
This really can only be one of 4 rearends. It could an 87-88 turbocoupe rearend, a SN-95 rearend, a 93 cobra rearend, or a stock fox rearend thats been modified with a disc set-up. Though all of these will bolt right in the first 3 are an inch wider than a stock fox and all of them require a disc brake specific or adjustable proportioning valve and I believe a different master cylinder. I think in your case the factory 93 Cobra master cylinder and proportioning valve would work.
The 87-88 Turbocoupe rears require some sort of hybrid cable system to make the parking brake work as the Turbocoupes used a foot pedal and the foxes used a hand brake set up.
Their are several right ups on swapping any of these rearends into a fox body just use google and you'll find them. Though first, I think the key would be to figure out the whole story on this rearend before you buy it. That way you'll know what your gettin into.
DJ