Series III, naturally asthmatic, turbo diesel & tdi's all have the same bolt-pattern for the bell-housing.
Make sure the clutch is the right one (spline-count), but the 200 & 300 are essentially the same on that front.
all but the early 300tdi engines require electonics, making the swap less pleasant.
engine mounts are different 200 to 300.... and you can mount a 200 onto the same mounts as a 2.5 diesel.
You'll need the intercooler, radiator & pipes for whichever engine you put it - they are all different
You'll need the exhaust pipe for whichever engine your fitting, that are all different.