you will need an engineers report, this you will then send to the insurance company . if youre local garage is an auto engineer then they can write you a report out and will not cost much . the report is to say that they have checked the vehicle and the work done is to a high standard and that the vehicle is safe to use on the road.
a rule of thumb as to what youre insurance will cost is that it will most likely be same as a vehicle in which the engine would have been originally fitted .
a landrover with a v8 in would be same insurance as a v8 landrover or range rover , a ford v6 engined landrover would be same as a 3 litre capri or 2.8 granada whichever type engine fitted and so on and so forth .
its best really to stick with a standard landrover engined vehicle and then youll only pay normal rates of insurance . a 300tdi engined landrover is only one group higher than the old 2.5 diesel version