Well, after searching for possible causes for a dead tach, the overwhelming response was to check the trailing igniter, and yep mine's dead. During my research though i ran across this https://www.rx7club.com/1st-generation-specific-1979-1985-18/tach-not-working-1985-gs-826572/ last post is the interesting part, has anyone tried this, if so, what were the results.

 

That last link is to a mod that's referred to as DLDFIS, or@GCFIS or a couple of other wierd acronyms and you should do a search for them. The mod converts the distributor wiring and signals to lower cost and stronger GM ignitors. Everyone says it makes quite a difference, I haven't done this yet but it's on my future mods list.

 

Here ya go. Check out post 298 I believe it is. https://www.rx7club.com/1st-generation-specific-1979-1985-18/easy-2nd-gen-direct-fire-install-20-minutes-243350/page12/
I would go ahead and do it to both ignitors that's what I'm gonna do on my carb'd 13b also I think Jeff20b has a writeup to do both ignitors and ford TFI coils.