What is your cranking compression?
Camshaft is on it's way out?
Not the same scenario as yours, but I had a miss @ different times,pulled out all plugs, all looked great & even,put them back in, get a miss @ different times, pull the plugs agian, all looked great, as I was reinstalling a plug, I felt a click in my hand. Hold the plug upright, then hold the plug down, "click" well the damm center porcelian (SP) collar would slide down & cover up the center electrode, causing an intermitant misfire.
What are you using for your ignition?, Points,HEI. worn out dizzy?
MBHD