1967 Barracuda 4 Speed 273 back fire issue

Ahhhh the memories, I used to own a completely orig 70 super bee and it did just about the same thing as yours, The problem was the result of two errors in wiring that were easy to correct. after numerous ignition, points, starter, alternator swaps I finally found the culprit(s). The ballast resistor smoking was my clue, the wiring from there to the fire wall connector had gotten discolored and while I was unwrapping the wiring at the firewall connector I noticed a little black stuff powdering out of the wiring. separation of all the wires and a full inspection revealed the connector had failed between a few contacts and started the ball rolling. As they would intermittently shorted to each other I had the same symptoms. acted like my timing chain had slipped..with your distrib reclocking I still wouldn't rule that one out!. anyway...I fixed the firewall connector and had great improvement..but still was acting funny, slow cranking and hard starts, would die..so looked more and found the ground from the block to the firewall just hanging...screw had dropped out of firewall. replacing that and hardware and my troubles were over. easy cranking, no more intermittent starter hangs, no backfires stalls or jumps.
Hope this helps, I am an aircraft electronic technician and most all of the problems I see boil down to wiring causing component failures.

Good Luck!:thumbup: