I don't have exact answer to your question, but it might help.
On this link:
Top 100 countries with sulfur
You have seen, that South Africa is in the golden middle of this ranking (ofcourse, it depends on the gas stations...)
This year, I was in Iran with my Hyundai Terracan, also equiped with katalyt converter. Iran, you can see on the map, is even more problematic about sulfur in the diesel (I could also smell it on every gas station there). No problems at all. I think also, the fuel filter does prevent a lot to put the sulfur in the converter and the engine itself so if you change it properly, I think you should not have some problems around. If there will be some problems, you can still plug of the sensor of the kalalyt converter and drive on.
My biggest worries are more about the vehicle engine, than on converter. But too less sulfur like in Europe is also not good for the engine, cause it's too dry.
I hope it helps!