What changed on the engine? I know there is a difference between valve covers / coil cover between early / late but I don't see that making a difference.

The only difference I know of is 91 ish M104 300sl / 300 CE had a distributor and later cars had 3 coils on 3 plugs and 3 wires running to the other 3.

Your 320 will have the later system with coils over the plugs.

The HT leads the first chap refers to must be for the earlier system with one coil, a distributor and leads. To whom I say, "Throw away the Bremi stuff and but the Beru lead set suggested above". My Beru set is still going strong after more than 5 years.

You could, of course, make up a complete lead set from the individual parts bought from MB. That, combined with ALL MB HT PARTS would be the best overall solution. Do make sure the cap, rotor and rear shield are in the best possible condition and, preferably, MB original.

All the best.

RayH

I suspect that the wire routing changed early in production.

Length for cylinder 1 changed from 490mm to 550, cylinder 3 from 240 to 350 and cylinder 5 changed from 430 to 550 mm. Wire ends at plug and coil also changed.