I illustrated the job
on my 1983 300SD. While the mounts for the 350SDL are different (left and right also differ), conceptually the job should be similar, with access maybe a little tighter on the 350.
Be careful to align the mount when replacing the bottom bolts or you risk cross-threading. I illustrate one version of a workable procedure.
You may want to check with 'gsxr', 'Jim SMith', 'engatwork' or 'Rick Miley' on the diesel section of this board - to name just four big body diesel experts.