danspann I sympathise, having just had to remove the warped exhaust manifold. I also have a 300tdi. Just as many miles but very few problems, also more economical, and with a few cheap tweaks, feels as if it runs as well as the TD5. Only rider to this, the TD5 drives an automatic, but people with manuals say they are greedy beggars. Considered doing exactly what you are doing, but the other problems on the td5 to do with chassis rust etc, put me off. So have now got a Disco 1 lpg manual, so the TD5 will be on the market very soon.
I expect you'll have massive ecu type problems, as TD5s have so many other "features" that 330 tdis never had.
Just my five pennorth!