hi Viper.
A method I have used many times and reliable operation is, go to your local car breakers yard and get a 'ballast' resistor.
Connect the ballast resistor in series with the +12v line that goes to the 'IGN' connector on the ignition coil.
Connect the collector of your 2N3055 transistor to the ignition coil that normally goes to the 'Circuit Breaker' contacts on the cars distributor.
Connect a high power, 24V 5Watt Zener across the 2N3055. The Cathode of the Zener to the collector of the 2N3055.
Connect also, the Res/Cap as shown in your original diagram.
DON'T connect a diode across the coil!!!
Design the 2N3055 base driver pulse circuit so that the transistor base current is about 200mA. Also make the 'dwell' time [the 2N3055 ON time adjustable] and the drive pulse rate adjustable.
Start with a slow pulse rate and the minimum ON time, use a an old car spark plug as a load for the EHT, adjust the dwell/ON time until you get the 'best' spark for the lowest ON time. Then adjust the pulsing rate.
[Remember the spark plug case must be connected to the ground rail of your circuit]
Do you follow this..