Got a LWB Station Wagon. Was originally a 2.6 6-cylinder petrol but a PO swapped it for a 2.25 diesel lump. Just replacing rear brakes and wheel cylinders and getting MoT'd. Tax exempt. Unsure to sell as is or fit a 200Tdi lump and 3.54 Range Rover diffs. If I did the engine swap, it would still legally retain it's right to tax exempt status.