If origina, your '66 will have an inertia starter and a remote mounted solenoid. The solenoid is powered by the white/red wire coming from the ignition switch. Nothing else connect to the white/red wire at either end. The white/red is not supposed to have any power on it at all unless you turn the key to the "start" position. There is nothing along that line to store any capacitance, it's just a wire.
On the early cars (that are set up for negative earth) a white wire goes from the "run" terminal on the ignition switch directly to coil (+). The aftermarket ignition will also have its red wire on coil (+). Power is not supposed to be on the white wire until the key is in the run position. There is no connection between coil (+) and the solenoid wiring... not on a car with standard, non-ballast ignition.
If the engine turns on its own for any reason you need to revisit the wiring paying particular attention to where each of the wires in this new loom are connected. If this is a loom for a later car with ballast wiring there are scenarios where there may be wiring problems. Again, more details of what your car has will help. And, did the car/engine ever run correctly once you installed the new loom?