Accidentally pulled Alt Blue Field Wire

Sounds like you have 2 field terminals on your alternator. 1970 was a transition year to that. The IGN feed comes from the key switch, thru the bulkhead connector. Perhaps the key switch terminals were zapped. It might have continued running because once a spark is started, it continues, but not enough contact in the switch to re-establish it. I think 1970 still had the key switch in the dash, so easy to remove. Once it was moved to the steering column (for lock), replacement become more challenging.