The 126 300SDL was available in Europe, the 140 chassis also shows S class diesels in my Bosch CD-Rom data system.
The 617 SDs were only available in the US. The only turbos in Europe were the Stationwagens.
The reason for this had to do with the US governments CAFE rules (Combined average fuel economy). Since MB customers weren't buying enough of MBs high mpg cars they had to make the base model "S" car have a diesel after 1977. Up till that time and always (till 1986) the base "S" car in Europe was the 280S/SE/SEL.
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician