The spark plug cap is removable, just twist it off and can be use on any other different degree spark plug caps. Use a multimeter: Primary resistance test, attach both positive multimeter lead and negative multimeter lead on the primary sides(input sides of the ignition coil). Secondary resistance test, negative lead on the output side(wire without the spark plug cap) and positive lead on the primary sides (both primary sides should get the same reading on the multimeter). Now you can twist the spark plug cap(or your old cap) back on(tightly) to do the secondary resistance test again. It should add another 5-10k ohms to the reading.