Since i'm contemplating replacing the timing chain, tensioner and its guide, and the famous chain rails, i have a few questions. First off, the patient is a '86 420SEL, almost all repairs done by me(radiator, front brakes, rear brake pads, fuel pumps and relay, and all maintence) with a tad under 160K. I can picture how to "roll" the chain out by using zip-ties to keep the new one from jumping a tooth, or use a guide made by Sir tools, the removal of the pivot pins, and the master link, but i have a few questions.
1. Just by looking at it, the driver's side chain rail does look a bit complicated to replace, is it easier to change it with the old chain loose?
2. Does the distributor have to come out?
3. since i will order the parts from Performance Products, and if the chain does come with a circlip master link, or the horseshoe one used on motorcycle chains, can i crimp it in its place?
Thanks!

it doesn't matter if its the old or new chain. yes you have to take the distributor out to replace the rails. no you don't need to crimp the clips.

This piece I wrote recently may help with the chain rails - it's on my 1990 560SEL - yours should be pretty similar, but check that you get the right parts as I am unsure whether the 420 uses the same rails.

I did not replace the chain as I had only 5 degrees of stretch at 100,000 miles.