...I am attaching a chart with some of the data on spark plugs.
Nice Chart! Superb effort and execution.
BTW the coil I use with the Pertronix is the Flamethrower II (in classic black of course). That puts out 45 kV.
The concept of the 123 is great, but my -051 was rebuilt in 2011, I installed the Pertronix at that time, and all has been well (ignition wise, at least!) since then...