I reread your symptoms and it's making me think it could be weak ground or poor connection somewhere.. intermittent symptoms are the most challenging but I wouldn't throw the baby out with the bathwater
I think it's worthy of a good diag or else you may be chasing it endlessly regardless of distributor type..
as for the resisted ignition wire, perhaps ballast resistors carry more stable current than what a factory coil needed? or it's deteriorated, degraded or failing in some manner?
could be worth a shot to grab a ballast resister and mock up a new circuit direct from b+ to see if the symptoms change/go away.. I would also suggest clean and confirm all connections, grounds etc.. could be all the way back in the key switch..
check the pickup coil to see if it's clean and clear where the shutter breaks the light beam.. I don't recall ever having an issue there but age, dirt, dust, etc in a truck environment may have migrated in there creating intermittent failure..
I have never called so not sure what you'll get but possibly call their tech line and see if they can shed some light on it (pun intended
) especially about the tach issue, that's got me puzzled.. I ran a 5" autometer without any glitches in my goat..
good luck and please keep us posted.. I have long range plans to repower my k20 burb with a 383 and the hei on the 350 in there now is riding the firewall
due to my past experience, I was considering a unilite or similar compact distributor and I am very interested in your findings, thank you!