I did this job over the weekend on my wife's 1981 380SLC - a 116.960 engine, converted to a dual row timing chain many years ago.
The job will be similar for the 116 5 litre and 117 4.2 and 5.6 litre engines.
Note that if you remove the distributor (to replace chain rails) on the early 3.8 litre engines, it has to be re-timed with an ignition light as timing is not electronic on the earlier cars. I will add illustrations on this soon.
An illustrated version
appears on my web site. The related change of rails (this was on my 1990 560SEL - again, the job on the 3.8 litre is very similar, though the 107 chassis affords far less working space) appears here