You may want to wait to see if your Pertronix and tach get along. I know it seems the usual deal is that the tach has a problem with the Pertronix but I had the opposite experience.
When I got my motor from Dave Bean many years ago, he had installed an optical ignition, I believe from Allison. I had pretty bad tach bounce above 3000 rpm or so. It gave out while I was in the left lane on the Interstate! I replaced it and the coil with Pertronix units and my tach calmed down.
I have no explanation but this does occur to me. Before I installed the gauges, I sent them to Nisonger to check them out. I didn't ask for anything than that but it's possible they do some upgrade on the tach as part of their checking it out but I don't remember any mention of it so I'd be surprised if they did.
Your supposed to use resistance plug wires with Pertronix. I got mine from Pertronix to make sure I got the right ones.