All good ways to test. If you don't get a good spark then something is going away. Normally when the MSD boxes I have had went bad, I got no spark. You could back track by taking the wire from the coil that goes to the distributor and see if it gives a good spark to ground. You should get a very good one as that is the high voltage side and watch for severe shocks, don't ask how I know. If that spark is weak then I would suspect the box or coil one. After you have followed all the above advise and checked the grounds as they are critical in these and any other electronic applications. I have never had an ignition switch go bad, but as stated above, they can fail. But once again I would think they would stop all voltage if the contacts burned or broke in them. The carry a complete back up set up is a good idea, especially if you drive out where it is miles to the nearest town or phone.
Ron
