It's not the wire that has the resistance it's the plug ends.
If they are Beru then the resistance tolerance specs should be written on them - 1 Kohm.

I would be more concerned if they were very dirty, appeared to be shorting out, wires hard and cracked. This would normally be representative of old leads. There is resistance in the distributor cap as well.

Do you have misfire problem?

However having said all that, - the best tuneup for a M103, is plugs, leads, dissie cap and rotor.

Plugs non resistive, NGK's or if you can still find them non resistive Bosch.