Pull the coil wire out of the distributor and check for spark there, pull the boot back and touch the wire end to the block.
If it sparks then coil is good.
Do the same thing with one of the plug wires, just touch the wire end to the block, never mind the plugs for now.
If no spark there its definitely cap/wire/or rotor issue.
If it has a spark there then only thing it can be is wrong plug gap.
You didn't blast the 6V coil with the 12V charger did you ?
Also does the block have a good ground ? 6V systems love good grounds!
Good luck!
