Not a gambling man, but my money is on the LED or photo sensor being thermal intermittant, as those vanes are too long in duration to be Hall effect or reluctance type design...!
I changed my old point system to optical system on my 67 Mercury Cougar...way back in the day...cost about $200 back then and lasted for about 3 or 4 years, before it "disinegrated" (distributor shaft runout caused the shutter to "guillotine" the sensor)so switched back to distributor/point system...more reliable and certainly would not strand you in the middle of nowhere. I would opt for a modern Hall effect aftermarket ignition system...not that much into nostalgia these days for shaky electronics design...but that is just me.
I changed my old point system to optical system on my 67 Mercury Cougar...way back in the day...cost about $200 back then and lasted for about 3 or 4 years, before it "disinegrated" (distributor shaft runout caused the shutter to "guillotine" the sensor)so switched back to distributor/point system...more reliable and certainly would not strand you in the middle of nowhere. I would opt for a modern Hall effect aftermarket ignition system...not that much into nostalgia these days for shaky electronics design...but that is just me.