64 Plymouth 273 Intermitent severe misfire.

What's your procedure for diagnosis other than throwin parts at it? Not bein a smartass, but until you actually DO some REAL diagnosis, you may well keep throwing parts at it. Have you done a compression test, for instance?
That's what I'm asking for. Some real diagnostic tips. Compression as far as I know won't cause an intermittent severe miss, or maybe you're just throwing that in there for extra pokes.