Right you are: a '77 280Z that until this year, was still running, after 200k mi., on the original distributor (with orig. pick-up coil) without incident.
But all good things must come to an end, and for the p-u coil, this resulted in ignition spasms that increased in occurence and duration of undrivable operation, until there was only a good idle with hellacious mis-firing (with much shake, rattle, and roll) at any revs above that.
Like you, I never suspected the p-u coil's fault and spent much time and money looking for the source of the ugly behavior. When it came down to "I've tried everything else", I bought the first replacement coil, the installation of which resulted in the very same behavior, so I kept looking elsewhere.
Three months later, I was back to "I've tried everything else" again, and I bought another replacement, thinking the crappy condition of the first upon receipt may have been more meaningful than I thought. Sadly, the second would not produce any spark at all. DOA. Mind you, all three passed the only test specified in the FSM, the check of resistance of the coil.
In between the two, I had purchased a "rebuilt" distributor body, as a despirate extension of my earlier "throw fresher parts at the problem" that resulted in a replacement ECU and ICM (among other parts), all to no avail. It was this distributor body that brought the p-u coil that looked to be out of some other application, along with some other oddities.
Finally, having little hair left to pull out in frustration after the utter failure of the second "new" p-u coil, I threw that puppy (the "rebuilt" distributor... (30Sep. edit)) in for lack of any other approaches to the problem. Lo and Behold, the engine got sweet once again! I was astounded. I moved the p-u coil to my own already rebuilt distributor (with its fresh cage and new bearing balls), and the engine is running fine once again.
There is a larger moral to this tale of woe; as a result of the violent behavior during the first p-u coil's recurring spasms of slow failure, the crank nose drive gears began to shear their keys and spun the distributor/oil pump drive gear press-fit on the spindle shaft. Fortunately, we're only talking a few degrees, and with the deployment of a new spindle shaft, I have been able to dial in a usable ignition timing for the time being; tho I know that when time and opportunity permits, I will have to address the crank drive gears in a more meaningful manner.
Thus, I urge you, Gentle Readers, to never take misfires lightly.