shiftSwitch
Sorry about the delay in replying. Standard Florida plague: Relatives from "up north".
PDF is basic layout. Many parts and connections not completed.
How it works: Fuse, coil, capacitor protect voltage regulator from nasties on the battery wire. Voltage regulator is set to provide +10 volts and protect all other parts from voltage nasties. When started, 10k and 1k charge up the first capacitor. The 10k resistor forces a delay of 3 or 4 tenths of a second after the lever switch is released (open). When shift lever switch closes, Cap charge is dumped to ground. This pulls down the voltage at the trigger input. The 1k resistor delays refilling for 5 or 10 milliseconds so the 555 chip has time to recognize the command. When the 555 recognizes the command, the output goes "high" and it times out 33 to 198 milliseconds using the 1k, 5k, and 33uf capacitor. Meanwhile, the MOSFET was "on" all the time. The 10 volt output of the 555 chip tells the little transistor to dump the gate voltage of the MOSFET. The MOSFET turns off, opening the ground on the "G" terminal of the spark module. The shift lever continues upward and shifts the gears. The shift lever is released and the first capacitor takes 3 or 4 tenths of a second to re-fill. Then the circuit is ready for the next shift.
I think this will work, but I expect several people will have comments about it.