Newbie needs help,my Duster won't start

I have a 74 Plymouth Duster. I can't get it to start. Had problems all last summer not wanting to start when it was hot. Then towrds the end of fall went to start it and it would just turn over but not fire. thought it was an extension of summer problems and not having a heated garage i gave up until today. thought it was a carb problem but it is getting fuel. so i checked a spark plug and no spark. distributer cap and rotor looked good so i checked the coil. the connections on coil are getting juice but no spark at the end of the coil wire. swapped coil with another one that worked last time it was used still nothing. so I tried another ballast and still nothing. could the ignition box be bad? anyway to test it? any other ideas? any help appreciated. thanks