Been working on my 69Z since bringing it back from the dead. Rebuilt carb, new gas tank, fuel pump, new plugs, flushed the fuel lines, new filters, new gas. Been running it every weekend for months, sometimes more. Today, go to start it up and she cranks but for some strange reason she doesn't catch. Then I get one hell of a backfire. Small amount of vapor/smoke comes out of drive side tail pipe for a minute or two after. Try to turn her over, nothing. Crank crank crank. Nothing. I try some gas in the carb, crank, she won't catch. Trying to figure out my next step here. Is it the coil? Timing out of whack? Points?