Essentially you want is to make sure you have 12V going to one side of the ballast resistor, then on the other side of the resistor you should have around 9V so you can take a wire from that point on the resistor and feed the positive side of the Ign Coil. Those coils only want 9-10V; if they are getting full power during operation they could be seeing 13 to 14 V because the system is charging which causes the coil to overheat and give a weak spark.

Another key part is that you want to have an "externally resisted coil" and a points based distributor. You can search YouTube on how to test what coil you have.



Also watch this video series from lively (a member here) made a while ago. This really helps explain it in detail.

https://www.youtube.com/watch?v=7LyJtyJPSEM When he had it wired wrong.

https://www.youtube.com/watch?v=9-N2OgZGpzo When he changed the wiring so the positive coil was only receiving power through the resistor.