Sign216 asks about whether substituting a transistor switch will improve the spark.
In general, the spark characteristics is generated by the coil characteristics.
It is well known that the ability to fire a spark plug plug improves with a reduced rise time of the spark voltage.
If you change the points from mechanical to electronic, but leave the coil as is, you will not see a significant improvement. In the attachment, in picture 6, is shown a typical 'Kettering' type of ignition coil. These types had a natural resonant frequency of around 1500 Hz and are quite slow. The development of high speed multi cylinder engines required better coil arrangements and this lead to coils with lower primary inductance and to limit the current at low speeds, a series, or ballast resistor was used.
I recently tested some Kettering coils and found the rise time was around 180 microseconds for a slow coil, around 150 microseconds for a faster coil, and around 120 microseconds for a fast coil. Each of these coils were used on 8 cylinder Chevrolet engines in a speed boat.
By contrast, when the change to electronic ignition and fuel injection took hold, the first change was to completely redesign the coil. The significant change was to change the magnetic circuit from the open long solenoid type used in the Kettering, to a closed magnetic circuit type used in modern engines. The closed magnetic circuit type significantly reduces the rise time. In the 1960's we built some close coupled ignition coils which had resonant frequencies of around 10 Khz, and these had rise times of 30 microseconds. If you look at an old type of ignition coil and compare it with one in amodern car, you will easily see the change in the physical proportions of the coil.
I havent checked any of the new coils, but generally as the rise time is reduced, the back EMF generated when the coil primary current is cut off is around 70 to 80 volt. The Mitsubishi car I drive has an electronic switch built into the distributor and when triggered, the electronic switch generates a constant width pulse to drive the coil.
There is a fair bit of optimisation that goes on with the ignition design, but generally the ADD ON types use more primary energy to generate a bigger, hotter spark which can cause spark plug deterioration at lower engine speeds. Typically, they do NOTHING to reduce the rise time of the spark voltage.
The modern designs use circuit arrangements and components which will give a uniform spark across the whole speed range of the engine.
In summary, if you change the points for a transistor switch, it is unlikely that you will see any performance improvement.
Hope this helps.