I too am somewhat at a loss, and would have called out plug, wire, cap, or optical disc obstruction. All that's been replaced.

Question. Are you checking spark at the plug, or at the distributor end of the plug wire?. Are you looking at the air spark at the plug tip or to engine ground? The only possible suspect I see is a poor plug ground to the head, which should be cured by a spark plug thread chaser application. ALso recheck the plug gap as installed. A very narrow gap may not ignite a lean warm engine mixture and show a weak spark snap.

Hook a vacuum gauge to the engine manifold vac and observe the needle movement at idle when cold and warm, and read up on interpreting vac gauge readings - good simple diagnostic tool. I've seen valves stick as an engine warmed up.

Test stuff by cooling it after the engine warms up. I used to use freon, but r134 will do. warm the motor up until you get the miss, then selectively cool stuff like the coil, dizzy body, power transistor, ecu, to check for a thermal fault in a component.