A coil selector would most likely just be a simple single pole double throw switch that is wired to a coil selector. No need for big amperage carrying wires or selector switches. Using a an automatic coil selector means you don't have to get out of the vehicle to swap coil wires - you still need the switch but you don't have to manually swap coil wires. You can save a ton of time by wiring in a switch... it's a whole heck of a lot easier to flip a switch than it is to get out of the vehicle and do it.... pull off the course, undo the belts, pumper, radio, climb out, switch wires, climb back in, hook everything back up, redo the belts, and drive off.