My advice would be to forget it. If you really want a diesel L322 with a 6-speed transmission then sell your TD6 and replace it with a 3.6 TDV8 (2007MY onwards). There are insurmountable mechanical issues with the conversion (different engine RFOB interface, torque converter not matched, different transfer box, etc.) but that pales into insignificance when compared to the electronic/control issues you would be faced with.
Phil