Mike at Autoprop will make you one. Just tell him Sierra diff and MT75 without the doughnut. He made me the adapter plate to fit the gearbox. The whole unit is 23 inches long, slider included.
Autoprop
Spinney Lodge, London Road
Felbridge, East Grinstead
Sussex, RH19 2RA
Telephone: 01342 322623
Fax: 01342 314947
Email: sales@autoprop-uk.co.uk