Strangely enough all my cars inc zetec mk1 have a Quaife ATB lsd. My mk2 which had 112kw@tyres has a ATB without a problem and it's been used on street for 14yrs ..I changed the oil every yr . The downside is they dont fully lock at high speed so if in a corner and a wheel lifts,, you will spin the wheel that's off the ground. Upside is wet weather driving is like normal except when you give it large you will swap ends if not ready to catch it. They are also quiet unlike the Ford Motorsport lsd...clunk clunk clunk on slow tight corners.

G`day guys
I found this somewhere on the web and thought i`d throw it into the fight.
 
It has been suggested to me by a notable Escort builder to run a diff from a mid 70s Volvo 240. Right width for a Mk2 with flares,5x108 PCD,comes with discs and LSD from a Jeep cherokee (Dana 30) will fit with ratios down to 5.3:1.
 
The only drawback i can see is that the volvo diff is heavy (dont know the actual weight)