Yeah, 8.8 is common in Explorers. If that's what you've got, the Mustang limited-slip carrier will work, provided the axle spline count matches up.
Just a word of friendly advice, though. The Mustang 8.8 Traction-Locs are pretty marginal. They don't provide a a good positive lock-up even when new, and the clutches wear quickly.
The reason why there's such a huge aftermarket of limited-slip units for Mustangs is the factory ones are so poor.
There are replacement clutches, springs, etc. for the stock units which help some. If you're on a shoestring budget, a fresh Mustang limited-slip unit is better than nothing, and certainly "good enough" for a weekend-cruiser. But in the long run, if you're going to the trouble and expense of changing carriers anyway, (and especially if you're going to be using sticky tires and/or throwing any serious horsepower at the differential) you might want to consider stepping up to a good aftermarket unit while you're at it.
Well that sounds like some sound advice. I know that 87 wasn't a hot year for mustangs mechanically either. I have a 9 inch in the yard waiting for a posi, I much rather save my money for that and put together right. I was just looking for a fun alternative until next summer....