Does this have coil in cap h.e.i.? Slim chance but it could be the module or pick up coil. Slap a parts store dizzy in it. Before tear down . Might get lucky. I had a bad msd box take out the guts of my dizzy 3 times before I got smart and junked the mad. I had similar symptoms. Not exactly the same but, might get you going before the weekend. If you have msd throw it in the trash or sell it to some kid .lol.
Still kind of limping around right now. Just back and forth to work when I have to take it. Should have the wife's truck back and complete by the end of the weekend. Then I'm going to pull the motor and go thru it all. If I find any issues other than the top end, thinking of going ahead then and doing a 383 stroker build on it.
With all the research I did trying to find one long enough to put the full tip into the chamber, I was surprised that AC didn't have one. Or I couldn't find it. I found very few that were the correct reach. Went thru several different ones from the parts store. They thought I was weird buying one spark plug of different types/brands. Once I told them why, they understood.
The NGK has a 18 MM reach, almost 3/4 of an inch. And the threads just reach the end of the threaded hole, which puts the tip completely in the combustion chamber, so no shrouding of the spark.
I was trying to find some E3 plugs that would work but couldn't find any.
So I started preping the motor to pull it in the morning. Got everything done but taking off the hood and pulling the motor.
Found #7 & 8 plugs are black sooty. So my issues may be in there somewhere.
I'm going to go completely thru the motor though.
Got the motor out and on the stand this morning. Found a few minor things in #8 cylinder. Pulled the lifters and found this. #8 exhaust is toast. Cam is probably wiped to. Still going to pull the pistons and look at them.