Hi
As I said, I put a 200 tdi in a Series 3
I used a 200 tdi out of a Defender as I was told the manifold on a Discovery comes out heading back this would mean cutting out a lot more on the passenger side foot well. All I had to do was cut about 2" off the inside corner.
I also welded some plates onto the chassis and then bolted the engine mounts straight through the chassis and plates. I then fitted the rad with some home-made plates and put in an electric fan between the rad and grill.
hope this helps