rear disc 5lug questions ... ????

I believe if you wish the run rear brakes off a 98 mustang you will need to change the rear track width since the brackets were designed for the wider setup. You will also need a newer style master cylinder and possible booster. You will need a brake proportioner for the rear and to gut the stock one on the new master cylinder. I think I remember seeing somewhere that you can get brackets to keep stock track width and run rear discs. You will also have to modify the brake lines on the rear too.

As for the ebrake cables- I believe summit sells ones that work with rear discs.

I personally would just get a sn95 rear and dump it in then just swap the mc/booster and add the proportioner and call it a day. But you can try and modify a stock fox rear if you wish. I believe its more expensive that way though.

http://svo73mm.cjb.net

you can get a set of brackets so you can use sn95 brakes with the stock track width but the brackets usually cost more than sn95 axles....
http://www.northracecars.com/catalog/brakes/brakes.htm

i have an sn95 rearend that is longer..and my 8's rub the fenders. not the best offset though. id go with the axels in the back, and a disc conversion that was meant for a fox. i had brakelines made by a local shop, and i still dont know how to get my ebrake working. but in the front ALWAYS go sn95 because 5 lug wheels are hard to come by that fit fox spindles.