Ok mate, I assume youve looked at the catalogue already, but here goes....

Defender 2.5 Tdi 250/300 came with a 240mm plate with a 25.4mm bore and 23 splines. The spline pattern was shared by the 3.5 V8 and the basic 2.5 but for some reason the TD5 used a 26.1mmbore and the same 23 splines. Various plate diameters were used, 241mm on the 2.5 and 267mm on the V8.

Ford sierra cosworth 10/87 - 10/90 (sapphire) had a 240mm plate, 26mm bore and 23 splines 10/89 - 03/93 was the same

The sierra 2.3v6 and 2.8v6 (xr4i and 4x4) (1982-93) both had a 240 mm plate with a 25.4mm bore and 23 splines so Id guess this is the one you need. The same plate is fitted to anything with an MT75x box by the looks of things, orions, mondeos etc.