An old time trick to make a country style version of the extender Volfandt referenced is to take a piece of leather, say a belt. Cut a piece a couple inches long...put a hole in one end that will slip over the porcelain end of the spark plug. Then you could pull the insulated end off the plug wire (careful to not pull off the metal clip) slip the plug wire into a hole you made in the other end of the leather. Now with great care position everything so the end of the plug wire is 1/4" or a bit more from the end of the sparkplug.
Now when #3 plug fires the added resistance caused by the spark jumping the gap will cause the coil to produce a hotter spark, causing the oily plug to fire. Probably.
With a bit of imagination you could do the above using an extended plug wire boot and just pull the wire out a sufficient amount so the spark has to jump a gap. Wouldn't have that old time look though.
Good Luck, RR
