Is the 1980 450SEL CIS injected?
Does this model require resistor equiped plugs?
Any suggestion on good plugs?
I am having problems with this car not giving a spark and considered replacing the coil as I believe this may be the problem. I have tested with a screwdriver at the plugs and I see no arcing from the ignition system. I have removed the cap from the distributor and it looks to be in good condition, no deposits on the points/blade. Are there any other tests I can run to isolate the problem? Help is greatly apreciated.

MB never used resistor plugs.
Test for trigger signal from ignition module to coil. You can use a test light on negative side of coil. Should flash the light durning cranking.

Do it right. Get the manuals. Benz makes some very, very fine manuals. All of the books for you car are collected on one CD for about 99$. They cover chassis, engine, Electrical, climate control.

-CTH