Help Junkyard coil for HEI distributor?

To test this coil, just :
1) Make sure 12v is on the proper primary side terminal
2) Connect a jumper to the other primary side terminal, and, while being careful to not touch the other end, just touch that other end for a fraction of a second to ground. The wire should make occasional brief contacts and make some decent sparks but not have long charging times.
3) Don't test at a plug, because you are adding in all the possible problems inside the distributor cap. Test at the far end of the spark wire from the coil (at the end that would normally connect to the distributor cap center post). Place it 1/4" to 3/8" from metal and watch for a good blue spark there.

OP, you need to understand that looking for a spark across a .040" spark plug gap in open air is meaningless. Jumping that small gap in open air is takes very low spark energy. It takes many times higher spark energy to fire the compressed fuel-air mixture in the engine. So that is why you test in open air to see if it will jump at least 1/4" to 3/8".