What kind of distributer setup do you have? If the timing isn't off by 180, possible something wrong with distributer setup. You say it ran once which leads me to think maybe it's a fried wire, like the black one from the distributor to side of the coil(little wire, not plug wire). That is what plagued me with my 71 429 when it wouldn't start. I replaced the wire, and bammo, houston we got ignition!