[Old Henry]

Just to make sure the problem wasn't in the new plugs, I switched the plugs from the cylinders that were firing with the ones that weren't. The problem stayed with the cylinders, not the plugs. So, they're all OK.

Because the distributor was creating reliable spark from the coil but the sparks weren't making it to some of the plugs, I decided to bite the bullet and replace all wires, distributor caps (inner and outer), and boots even though I could not see any sparks in the dark from the wires. Hope it fixes the problem. All of those new parts ain't cheap.

Thanks to all who made an effort to consider and advise.