My w126 300SD (the 617 turbo) has and will run at 120C all day if the outdoor heat, driving conditions, and AC status warrent it.
With the AC on, sitting at idle in my driveway in about 80 degree weather...the temp will climb right up to 120 then the AUX fan will kick on and keep things between 110 and 120.

With the AC off, sitting at idle, same conditions, 100C is common with no AUX fan operation.

AC on or off, crusing temps vary from 90-110C depending on outside conditions and AC operation...nothing fantastic.

Keep your 617 turbo out of the red and you are fine. Period.

P.S. Just make sure your cooling system compoents are up to snuff!