the alt would energize the coil when the starter was engaged even if the key was off, you don't want power directly to the coil, it should be switched - the power from the alt should go to the battery, power for other things comes from the battery terminal on the starter .... a 12V conversion doesn't really change anything, with the regulator out of the picture the rest of your 12V wiring should be the same as the factory schematic
Bill
