Have a look at Benzworld and in particular this thread:
https://www.benzworld.org/threads/pertronix-install-with-and-without-switchgear.1714668/

If ignition module is bad, then you will need to bypass it and install a Flamethrower coil as described. Also add a resistor to get tach to work properly. All described in that link.

I have had one of these installed for a long time - maybe 16 years!

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Graham
85 300D,72 350SL, 98 E320, Outback 2.5