backfiring through carb

1. Is this a point type distributor?
2. Is the gap ok? .018 to .020 I think! Dwell meter about 40 to 45 degrees [running...thats the problem!]
3. Timing @ idle: TDC to 5 degrees BTDC...10 degrees if you can get away w/it!
4. Plugs are now fouled out...black as can be! Hence the reason for the back fire
5. When you get the engine running and things close, check the voltage @ the coil positive, it should be between 9 and 10.5 [engine running @ idle] If the voltage is too low, the coil will not produce a sufficient spark...especially if the points are not making good contact/ground. Coil saturation can only occur if the voltage is sufficient/ground is good and dwell is w/in specs!
Good luck.