coil spark jumping outside to ground ??
 

Have a freshly rebuilt 2.0 liter with new distributor cap, wires, points, though using an older used 12v coil from USA. Ran well first 200 miles. Yesterday I noticed with engine running, a steady spark jumping out of coil "outlet" nipple and, shorting over to both positive & negative posts of coil. Engine continues to idle though.

Any guesses as to why brand new parts are allowing this to happen.

The high voltage from the coil will seek the path of least resistance. I would guess there is something on the outside of the coil that is conductive. Dampness or conductive grease perhaps? Or, if your high voltage coil lead has high resistance, faulty terminals, or the terminals aren't properly seated on either end, that might cause this.

The coil is cracked or internally shorted