Ive got the engine way overcarbed so I dont need to kill its coil to give it enough unburned fuel to light up for one thing. Ive got a switch thats connected to the battery to the toggle under the steering column, then it runs to the coil mounted in the trunk. Then you just drill a hole in the tailpipe and screw in a long necked spark plug and run a plug wire from it to the coil. Ive got the plug about 8 inches from the tip so the flames are only about 10 inches long. If the pipes thinner and if the plugs closer to the end youll get a bigger flame.
I could never afford one of those kits to do it so I just built mine and played with it till it worked. On the funny side ater I set the grass on fire I started testing it on the driveway instead of the backyard!