faulty spark plug????
 

Also posted at Samba.
Bottom line, the spark plug in #2 has gone bad three times in the last 300 miles. My '64 convertible drives around town only. Most trips are 3-5 miles. I have replaced the #2 spark plug for the third time in 300 miles of use over 2 summers. The symptoms are the same each time....engine runs like a champ on the new plug, then after about 50-70 miles of multiple short trips of 3-5 miles each, cylinder #2 stops firing. I replace the plug, and it runs like a champ again for 50-70 miles of short trips. What could be causing this?

What colour are the spark plugs when you take them out that will give an indication of how its burning?

The HT cables are wire the suppression is done by the plug caps. Check the resistance of all HT leads. The plug cap resistance which unscrews should be about 20k Ohms, Check for any cracks in the distributor cap and you have the spring loaded carbon centre contact.