just get an IB5 box from a zetec and fit the lsd on it, i done the conversion on mine, a reconditioned IB5,with my rst final drive and lsd, fitted at a garage, for £285, they supplied the box, i supplied the clutch, never gave me any problems or my mates rst,

we were both running over 200bhp for about year with no problems including many runs at santa pod, make sure u get the box which has the starter at the front of the box