[Will N]

I think this point that you made is telling:


"-I was told that the points were not generating the spark. That issue allows gas to accumulate and produce the big backfire."





Do you have the "wireless" bottom plate in the distributor. You probably do as you mentioned that you have the modern points. Those wireless bottom plates are prone to trouble. How they work is that there is a springy brass bus and an acorn nut or a L shaped shoe that makes contact with the bus and brings power to the points. That springy brass can lose it's springiness, and then it will not make good contact with the acorn nut or shoe, causing intermittent loss of spark. When the contact reestablishes itself, the spark will return and it will light up all that unburned fuel in the muffler. I would change the wireless lower plate to the original style wire that runs directly from the lower plate to the points. Fewer moving parts to go wrong.