I believe if you want to put a turbo in take the 352T. If you take the 366, then you also have to change the axles, you must take the fast axles. My 1300L got no turbo and I don't want one. My Diesel consumption is between 19L and 20L. per 100 Km. If I use my Split, then I need about 21L-22L.
The cylinder head of 366 is the same as 352. You can build the bloke also in the 1300L without a turbo.
I have no personal experience, but from what I've read on overseas forums (Benzworld, Expedition Portal, etc) the later 1300L ambulances with OM366 motors and fast axles are very desireable. Much faster average cruising speeds than 1300L's with the OM352 and slow axles.
The combination of the 366 turbo and the fast axles not only gives a higher top speed (up to 100km/h compared to 80km/h of the non turbo OM352), but they also fare much better on maintaining their speed on hills.
If you're intending to use the mog as a touring vehicle, considering the long distances we normally travel on trips here in SA, I would think the OM366 with fast axles is a very desirable option.
Also - the OM366 / fast axle combination (if an ex military ambulance) is a standard Mercedes option on these vehicles, which should make ordering spare parts a simple process, whereas any conversion will complicate the ordering of the correct spare parts.