when you say differential I'm assuming you mean the housing and not the actual differential (Carrier)?

As stated,.. the Fox and 94 - 98 8.8 housings are identical width. The SN95 has an extra 3/4 inch per axle to make room for the ABS exciter rings which are located externally of the housing itself.

The 99 - 04 8.8 housing itself is wider than both the fox and 94 - 98 cars. As are the axles.

As for the carriers (Differentials),.. 8.8 is an 8.8 is an 8.8. They all interchange provided the spline count matches the axles.

You can use Fox width axles in a 94 - 98 housing. How ever,.. the caliper brackets need to be flipped in order to retain disc brakes. Else just swap over the Fox ends for drums.

The problem with using SN95 or 99 - 04 width axes and rears (As I'm sure you've already discovered) in a fox body is that it severely limits your wheel choices on the rear. 9" wide wheels will fit,.. but they will rub the fenders. 10" wide wheel will stick out past the fenders. Using fox length axles you can fit up to 10.5" wheels and 315 tires (Depending on brand) and still keep them tucked inside the fenders.

I'm running into a similar problem with my set up. Because I have coil overs on the rear, the coils intrude slightly into the wheel well. I have to stay with a 10" wheel and instead of using the traditional 6.5" BS. I have to use a 6" BS. I wanted to stay with 17" wheels but it was difficult to find a 10" wide wheel in a style I liked with the BS I needed. I found that 18" wheels are loaded in 18x10 combinations and 6" BS is quite common. Will be using a 295 tire on the back of mine.

Hurst