Re: diesel engine swop
first check should be the numbers on the injection pump, range rovers and vaux omegas and some bmw cars had the part number ending in 994
bmw had various different numbers and none of these will work on a p38 the electronics are different.
to make it worse bmw also had different size holes that the pump sit in small hole and large hole (p38 large hole) small hole engine can be used but pump has to be machined down to fit or the electronics from the 994 pump needs to be swapped by a pump specialist onto small hole pump. some people have swapped the electronics themselves but not something i would recommend as the are set to hundreds of a mm, to far out wont rev up to far out the other way will rev itself to destruction.
apart from that sump has to be changed and use your manifolds and turbo etc