Welcome!
Sorry to hear about the Chevy
When my car did the same thing, backfiring, I went back through the the ingnition, checking the gaps on the dist, in the dist and went through the timing again. The problem went away.
I scared the hell out of my wife before I fixed the problem. I drove the car into the garage. Turned off the car by reaching in through the window, ran into the house and yelled duck, then the car backfired.
