You can test spark plug wires for continuity and resistance (usually something like 1000 ohms/ft for carbon-type conductor, or it used to be), but the main issues can be arcing to ground through the insulator, which no resistance check will find. If there might be some cracks in the internal conductor, it's possible for the coil to fire through them just as it does the regular spark plug gap, BUT it will cause more current flow thorugh the cap and rotor and other ignition components to make that happen which can cause other failures.
Basically, the spark plug and wires need to transfer as much of their original energy to the initiation of the spark in the combustion chamber. Many of the more modern spark plug designs address reducing the voltage power consumption of the spark plug. Making more efficient use of this energy makes the job of the rest of the ignition system a little easier plus not having to have super gazillion voltage ignition coils. The coil's only going to produce as much energy to make the plug fire as it needs to, even if it might be rated to 50,000 volts output. Keeping those voltage requirements low is a good orientation.
An older vehicle might not have to pass any emissions tests for where you live, but that does not mean we should condone "gross polluter" vehicles either. An older vehicle can be tuned to run pretty dang clean at idle and also out on the road too. Usually takes just a little finer tuning and/or some fuel system cleaner. Shopping for plug wires of more modern designs and materials can also yield some that are of the correct color/color combination for vintage vehicles too.
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