Strange SC no start issue solved....
 

After going through numerous threads and troubleshooting by the book, my non-factory type worn out key seemed to be the problem on my no start '82 SC.

I had (luckily) made a copy on an original type blank after I purchased the car. The new "copy" seems to have done the trick. If all else checks out on a no start issue, try the spare key!

So your no start was not being able to turn the ignition switch (engage the starter) with the old key?
Or was the switch turning but not starting?

Most of the time the key would insert and turn, but was at times difficult to move and it would "click," but not turn the engine over. Every once in a while I would have to gently move the key a bit in or out to turn it and it would fire, or bump it back and forth - some times it just would not fire, only click.

I think at some point the key became worn enough to not properly engage the switch. I cleaned the grounds (batt/trans) and replaced the electrical portion of the switch, checked the voltage at the starter, but that's as far as I got before the replacement key was put into service and solved the issue.