[Rev]

I think the way it was done way back when was to mount a coil in the trunk with a spark plug wire leading to a spark plug mounted a foot in front of the exhaust exit. Then a toggle switch was used on the dash to send juice to that coil that supplied that spark plug. Extra gas would be in the exhaust especially when letting off after reving up. Switching the toggle switch off and on would supply the spark to light the gas laden exhaust and create the pyrotechnics. I never did this but I think that's how it worked.

Rev