Could be plug wires or the coil wire. Even if the dizzy stays dry inside, if the plug wires get wet they will short to ground and the plug for that wire wont fire. If it goes from not running to running in a relatively short time (less than 30 mintes) look for these types of issues. The plug wires dry out faster due to the engine heat and exposure to open air. If you get water inside the dizzy, it usually takes longer to dry out.
Randy Rosetta KDØKWX TLCA #19351 69 FJ40 "Meanie" & 1970 Boss 302 Mustang