If he has a "remotely" precise dist, properly timed, and using a quality coil, there will be no misfires due to running a 0.045 inch plug gap. That said, we are still holding some assumptions and he must be using properly gapped, new spark plugs of sufficient quality.

Once a sparkplug has been fouled, it is not ever the same.
Since he has had at least two distributor failures, has run with the "improper" plug gap,and likely also has some air/fuel mixture issues- Yes, those plugs are going to misfire. Now, it will not be a "dead" miss as if a cylinder dropped out, and many would not say that the engine is mis-firing-However, an O-scope would show you that you have some ignition issues.

I would "feel" the difference.